Cross-cutting
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The eight protocols side by side on the same dimensions. Every cell carries a value, a confidence and its sources. A cell may read “not published” when the source shows that nothing is public.
34 dimensions, 272 filled cells (256 verified, 13 reported, 3 unverified). Select a citation marker to open the source details.
Matrix
Showing 34 of 34 dimensions for 8 of 8 protocols. No group filter applied.
| Dimension | ERC-8004 | x402 | Visa TAP | OpenAI ACP | UCP | Stripe MPP | AP2 | Mastercard Agent Pay |
|---|---|---|---|---|---|---|---|---|
| Overview and governance | ||||||||
| Primary job | On-chain agent identity, discovery and public feedback Three registries: identity (ERC-721 plus a registration file), reputation, and validation (specified only). | Pay-per-request payments over HTTP 402 The server prices a request in a 402 response, the client signs a payment, a facilitator verifies and settles it. | Agent identification on merchant web requests The agent signs each request with RFC 9421, tagged browse or pay, and may add signed consumer and payment objects. | Agent checkout against a merchant-hosted API, with a scoped delegated card token The agent creates, updates and completes a checkout session; Delegate Payment swaps a card for a vault token bound by an allowance. | Agent checkout, carts and orders with capability negotiation Discovery at /.well-known/ucp, negotiation, then checkout over REST, MCP, A2A or embedded. | Pay-per-request, metered and recurring payments as an HTTP authentication scheme 402 challenge, credential and receipt; methods settle on their own rails. | Signed mandates that prove what a user authorized an agent to buy Checkout and Payment Mandates, closed or open, verified by merchant, credential provider and processor. | Let registered agents pay with scoped card tokens Network registers agents, issues agentic tokens and lets merchants recognize agent requests. |
| Layers covered | Identity and trust; reputation and feedback; discovery No checkout, authorization or settlement layer. | Settlement rails and payment credential; discovery through Bazaar; refunds only in auth-capture No identity, intent or checkout layer. | Identity and trust; carries payment credentials at checkout No settlement, consent or dispute layer; those sit in VIC and card rails. | Checkout and orders, payment credential handoff, discovery and feeds, post-purchase order events No agent identity, reputation or user mandate layer. | Discovery, checkout and orders, payment credential handoff, identity linking; mandates only through the AP2 extension No settlement rail of its own. | Payment credential and settlement rails; optional discovery No identity, mandate or checkout layer; disputes depend on the rail. | Intent and authorization; payment credential scoping; dispute evidence No rail, no checkout messages, no identity registry. | Payment credential, identity and trust, intent Tokens, agent registration and signatures, Verifiable Intent for intent. |
| Stewards | ERC-8004 team (community), coordinated by De Rossi (MetaMask) and Crapis (Ethereum Foundation) Co-authors Jordan Ellis (Google) and Erik Reppel (Coinbase); no foundation found. | x402 Foundation (Linux Foundation); TSC: Coinbase, Cloudflare, Stripe Originated at Coinbase Developer Platform. | Visa (developed with Cloudflare) | OpenAI and Stripe (founding maintainers); TSC: OpenAI, Stripe, Meta Meta joined 2026-04-24. | UCP Governing Council; Google and Shopify permanent, Stripe elected Google is custodian of ucp.dev. | Tempo Labs and Stripe Rails maintain their own methods (Visa, Lightspark, Circle and others). | FIDO Alliance working groups; Google for samples and SDK Donated 2026-04-28. | Mastercard Verifiable Intent maintained by Mastercard and contributed to FIDO. |
| Governance model | ethereum/ERCs editorial process; contracts controlled by one proxy owner An EIP editor returned the text to Draft on 2026-01-13; one externally owned account owns the proxies on Ethereum and Base (2026-10-11). | Foundation under an LF Projects technical charter TSC with one vote per representative and majority decisions; 75 percent supermajority for Core Principles. | Proprietary Visa specification Visa changes it alone; licensees apply updates within six months; Visa says it will align with IETF, OpenID Foundation and EMVCo. | Company-led TSC of up to 7 seats appointed by the founders; SEPs by simple majority; founders' block-only veto No foundation; one is a stated long-term goal. | Council-owned, no foundation; Google proxy for open seats until December 2028 Domain Tech Councils of 16 seats, some permanent, decide by majority. | Core as an individual IETF draft; methods by rails; no foundation No working group, charter or steering committee. | Industry alliance working groups (FIDO) Payments Technical Working Group chaired by Mastercard and Visa; no public deliverable yet. | Proprietary network program No public spec, version or governance body; VI is open at FIDO. |
| License (spec and code) | Spec CC0; contracts MIT per file headers (README says CC0) | Apache-2.0 No separate docs license found; contributions need GPG-signed commits. | Visa Developer Center Terms plus TAP Product Terms (revocable, no modification) Sample files carry MIT-style headers, conflicting with LICENSE.md. | Apache-2.0 Contributions under a corporate or individual CLA. | Apache-2.0 (UCP Authors) Contributors sign the Google CLA. | Specs CC0 1.0; tooling Apache-2.0 or MIT; mppx MIT IETF submissions fall under IETF Trust terms. | Apache-2.0 Repository license covers docs, schemas and code. | Program proprietary; VI Apache-2.0 Acceptance Framework spec not public. |
| First announced | 2025-08-13 (created) Merged into ethereum/ERCs on 2025-08-18. | 2025-05-06 Whitepaper and npm launch. | 2025-10-14 | 2025-09-29 With ChatGPT Instant Checkout and Stripe SPTs. | 2026-01-11 Launched at NRF. | 2026-03-18 With Tempo mainnet; spec repository created 2026-01-05. | 2025-09-16 Google Cloud launch post. | 2025-04-29 |
| Latest version and date | Draft text of 2026-01-25; contracts 2.0.0 | Spec v2.0 (2025-12-09); @x402/core 2.28.0 (2026-09-29) V2 launched 2025-12-11. | No version number; launched 2025-10-14 Sample repository last changed 2025-10-28. | 2026-04-17 (dated folder) No GitHub release or tag; folder edited after release (2026-05-01, 2026-06-15); last commit 2026-07-18. | v2026-08-25 (2026-08-25) main carries drafts; SDKs 0.5.x match it. | draft-httpauth-payment-01 (2026-09-09); mppx 0.13.4 (2026-10-08) Old name draft-ryan-httpauth-payment expired 2026-09-18. | v0.2.0 (2026-04-28) main idle since 2026-04-29. | Unversioned; VI 0.1 (main 2026-04-20) Latest program addition: Trust Framework, 2026-09-30. |
| Maturity | Draft ERC; Identity and Reputation live on 25 mainnets; Validation not officially deployed README list as of 2026-08-15, unchanged on 2026-10-11. | Live (V2 since 2025-12-11) upto, batch-settlement, auth-capture and Lightning are 2026 additions with uneven SDK coverage. | Live at named merchants, still in development Live European purchases 2026-07-02; overview says development and deployment, not in all markets. | Beta spec, Draft RFCs; deployed for feeds in ChatGPT 2025 in-chat checkout scaled back in March 2026; payment sheet in private beta. | Live on Google AI Mode and Gemini (US) since 2026-02-11 Four dated releases; AP2 extension live use unverified. | Live deployments on a draft spec Tempo mainnet and Stripe since 2026-03-18; Stripe docs labeled Frontier; no IANA registrations. | Draft specification with samples No verified production use. | Pilots or first transactions Network-level enablement in Europe since 2026-06-02; named transactions controlled. |
| Mechanics | ||||||||
| Transports | EVM transactions and reads; files over IPFS, HTTPS or data URI; /.well-known domain proof | HTTP headers, MCP _meta, A2A task metadata The facilitator API is HTTP in every case. | HTTP headers and request body No published MCP or ACP binding. | REST over HTTPS, MCP binding (5 tools), webhooks, feed API and files MCP binding released in 2026-04-17. | REST, MCP, A2A, embedded OpenAPI, OpenRPC and Agent Card descriptions. | HTTP authentication headers; JSON-RPC and MCP; SSE receipts MCP error -32042 and _meta credential and receipt. | Transport-agnostic inside a commerce protocol UCP extension; A2A in samples; OpenID4VP and the Digital Credentials API for delegation. | HTTP signatures, card forms, merchant APIs, card authorization |
| Settlement rails | None (moves no money) Registries live on EVM chains; payments happen on other rails. | EVM chains, Solana, Lightning and other CAIP-2 networks; credit-backed cloudflare:402 Fiat ids such as ach:us appear only as examples of the id format. | Card (Visa network) TAP itself moves no money. | Cards (FPAN or network token) through the merchant's PSP; seller-backed gift cards, points, store credit SPTs can carry Link, wallets, Klarna and Affirm on Stripe. | Rail-agnostic handlers; cards via the merchant's PSP in practice Credential types token, PAN, network token. | Tempo and other chains, Stripe SPTs, card networks, Lightning 11 method ids in the spec repo; mpp.dev documents two more. | None of its own (rail-agnostic) Cards, bank transfers, PISPs and x402 via a2a-x402. | Card rails; AP4M adds accounts and stablecoins |
| Agent identity model | ERC-721 token per agent pointing to a registration file; global id agentRegistry plus agentId | None in the core; optional extensions sign-in-with-x (CAIP-122), auth-hints (OAuth 2.0 with DPoP), RFC 9421 agent signatures in cloudflare:402. | RFC 9421 signature with a key registered by the payment scheme Key store at mcp.visa.com/.well-known/jwks; onboarding not public. | Bilateral bearer key per agent and merchant pair Detached Signature recommended; no registry or key directory. | Domain-based platform profile plus JWK keys; RFC 9421, OAuth, API key or mTLS Authenticated principal must be bound to the profile in UCP-Agent. | None in the core; optional request attestation in mppx Optional DID source; Web Bot Auth and TAP profiles; TAP headers optional in the card method. | Proof of possession of the agent key in cnf Agent identification left to the commerce protocol. | Registered, certified agents; RFC 9421 with tag Agent-pay-auth Key directory location not public. |
| User authorization model | None No consent or mandate object; ERC-8226 (Draft) proposes one on top. | The client signature on each payment No user mandate object; AP2 mandates can carry x402 through a2a-x402. | None in TAP; passkey-approved Payment Instructions in VIC The ID Token can carry auth_time and amr. | Buyer confirms in the agent UI; token limited by an allowance No signed mandate or consent object. | Buyer places the order in a trusted UI; optional AP2 checkout mandate Identity linking with OAuth 2.0 for signed-in actions. | The client's payment proof per request, or a rail grant Session deposit, SPT limits or Tempo access key; no user mandate object. | User-signed mandates (SD-JWT VC) on a non-agentic Trusted Surface User Credential or Trusted Agent Provider delegation. | Consumer consent with passkeys; optional VI user-signed L2 |
| Human-present and human-not-present support | Not applicable Registries record identity and feedback, not purchases. | Both Built for unattended clients with SDK spend controls; @x402/paywall serves humans; AP2 ships human-present and human-not-present x402 samples. | Agent acting for a consumer who approved an instruction in VIC TAP has no presence indicator. | Human present Every flow assumes the buyer confirms in session; no delegated standing authority. | Human present by default; human not present only with AP2 (specified, unverified live) | Both Built for unattended clients; browser wallets should ask a human to confirm; SPT creation may prompt 3DS. | Both Closed mandates for human present; open mandates with constraints for human not present. | Both VI Immediate (user present) and Autonomous (agent delegated) modes. |
| Merchant of record | Not applicable No payment flows through ERC-8004. | The resource server In cloudflare:402 the network (Cloudflare) is merchant of record. | The merchant TAP does not change who sells. | The merchant OpenAI and PSPs are not merchant of record. | The business Google and Microsoft are not merchant of record. | The resource server With the stripe method the seller's Stripe account receives the PaymentIntent. | Unchanged: the merchant AP2 adds no intermediary that takes over the sale. | Merchant stays merchant of record Normal card acceptance through the merchant acquirer. |
| Credential type | ERC-721 token plus EIP-712 or ERC-1271 wallet-binding signature | Signed payment authorization EIP-3009 or Permit2 signatures, ERC-7710 delegations, a partially signed Solana transaction, or a Lightning preimage. | Agent signing key; VIC agent-specific network token in the payment container Credential hash, encrypted payload or browsingIOU depending on processing path. | Single-use vault token (vt_) or Stripe SPT Network tokens can sit under SPTs. | Opaque handler token, PAN or network token Google surfaces: Google Pay PAN_ONLY. | Bearer Payment credential wrapping a method proof Signed Tempo transaction, SPT id, JWE network token, Lightning preimage or EIP-712 voucher. | Payment token scoped by a verified Payment Mandate Issued by the Credential Provider, possibly with the network. | Agentic network token (plus Virtual Card Token with DTVC) |
| Cryptography | EIP-712, ERC-1271, keccak256 file commitments ECDSA recovery also accepts EIP-7702 delegated accounts in the reference code. | EIP-712 typed-data signatures; Ed25519 for RFC 9421 and Solana; SHA-256 preimages on Lightning Smart wallets through ERC-1271 and ERC-6492. | RFC 9421 (Ed25519 in examples), PS256 body objects, JWT and JWS ID Token | TLS; HMAC-SHA256 webhooks; optional detached request signatures (Ed25519 or ES256 examples); 3DS2 Signature algorithms agreed out of band. | RFC 9421 with Content-Digest; ES256 baseline; JWS and SD-JWT in the AP2 extension | HMAC-SHA256 binding, JCS, RFC 9530 digest, EIP-712 secp256k1, JWE RSA-OAEP TLS 1.2 or later required. | SD-JWT VC with ES256, Delegate SD-JWT chains, SHA-256 hash bindings JWK type fixes EC P-256. | Ed25519 or ECDSA P-256 request signatures; ES256 SD-JWT for VI; DSRP cryptogram |
| Discovery mechanism | Registration files with services (A2A, MCP, web, ENS, DID), indexed by explorers and subgraphs | Bazaar extension and GET /discovery/resources Public CDP Bazaar; x402scan reads /openapi.json and /.well-known/x402. | Visa key store (JWKS); Agentic Directory announced No public directory list found. | /.well-known/acp.json per seller; push product feeds to the agent No public registry. | /.well-known/ucp business profile No public registry of businesses. | Optional /openapi.json with x-service-info and x-payment-info No .well-known path; mpp.dev directory and MPPscan. | None of its own; UCP /.well-known/ucp lists the extension | None for merchants; key directory for agent keys |
| Controls and risk | ||||||||
| Replay protection | Partial: EIP-712 domain and a 5-minute deadline on wallet binding, no nonce | Single-use nonce plus a validity window, enforced by the token contract Replay stores for Lightning payment hashes; cumulative vouchers in batch-settlement. | 8-minute window plus nonce; nonce tracking optional | Mandatory Idempotency-Key; one_time allowance; 300-second webhook window Request Timestamp checks only SHOULD. | Signed Idempotency-Key, 24 to 48 hour storage, 409 on mismatch | Single-use challenge ids and single-use method proofs Idempotency-Key, digest binding, channel and domain binding. | checkout_hash, transaction_id, sd_hash and cnf; one presentation at a time No consume-once rule for verifiers. | Nonce and window on signatures; single-use tokens and DTVC |
| Native spending controls | None (moves no money) | None in the protocol; SDK default of $1 per payment Budgets are out of scope in the spec; upto signs a ceiling. | None Limits live in VIC. | allowance.max_amount and currency per token Plus merchant, session and expiry scoping. | None in UCP Caps come from AP2 mandates, the wallet or the platform. | None in the core; caps come from rails Session deposit, SPT usage limits, Tempo access keys. | Yes: payment.amount_range and payment.budget Plus payee, merchant, instrument, PISP, line item, date and recurrence constraints. | Token limits by merchant, amount, time; VI amount_range and budget |
| Revocation | Feedback revocation by its client; wallet unset; no identity revocation or burn | None for a signed exact payment before it expires auth-capture adds void and client reclaim; channels allow timed withdrawal. | Key removal or expiry only No revocation list or status endpoint. | None in the spec Stripe SPTs can be revoked; sessions can be canceled. | Key removal from the profile; RFC 7009 token revocation for identity linking | No core revocation; method-specific cancellation; forced channel close | None; expiry only The spec recommends the shortest exp. | Not documented No public revocation API; VI 0.1 has no revocation protocol. |
| Refunds and disputes | No disputes; appendResponse can show a refund | No refunds in exact; no dispute process auth-capture refunds; third-party x402r for refunds and arbitration. | Not in TAP; card dispute rules and VIC signals No agent-specific liability shift published. | Merchant handles refunds and chargebacks; order adjustments report refund, return, dispute No dispute protocol. | Order adjustments record refunds, returns and disputes; handling stays with merchant and PSP | Depend on the method Card routes keep chargebacks; Stripe stablecoin payments have no disputes; session close refunds the unspent deposit. | Dispute verification steps; no refunds Retention, retrieval and adjudication out of scope; liability with networks. | Standard chargebacks; no agent reason codes |
| Privacy exposure | Everything on-chain is public and permanent; files public if their URI is The text says on-chain pointers and hashes cannot be deleted. | Settlements are public on chain; resource metadata reaches the facilitator Header contents stay private between client, server and facilitator. | Consumer IP address, device data, country, postal code and obfuscated contacts reach each merchant No minimization or retention rule. | Buyer contact, address and risk signals go to the merchant; card data only to the PSP or vault Nothing public. | Platform sees buyer data, signals and order history; credentials are opaque Privacy and upselling concerns raised in a senator's letter (reported). | Chain settlements public; credentials private between client and server Card credentials may carry billing address and name; core forbids requiring accounts. | Low by design: mandatory selective disclosure of constraints risk_data travels to verifiers. | Agents see tokens, not card numbers; VI sub always visible |
| Published security research | Yes: an empirical study of Sybil reviewers and liveness; an unmerged community audit; no CVE | Yes: several 2026 papers and two high-severity advisories Five attacks, free-riding flaws, facilitator risks, A402, PII leakage, formal analysis; GHSA-3j63-5h8p-gf7c and GHSA-qr2g-p6q7-w82m. | None specific RAILS names TAP; the formal analysis of 2026-08-30 does not model it; no CVE. | Little: one formal model covering ACP among four protocols No CVEs or advisories; an audit-trail critique. | Two arXiv papers name UCP (2602.06345, 2606.05043); no CVE or advisory | Yes: one formal analysis and six SDK advisories Tamarin model in arXiv:2609.00060; CVE-2026-34209, CVE-2026-34210, CVE-2026-63627, CVE-2026-63628 and two critical GHSAs. | Yes: several 2026 papers; no CVE 48 threats (2608.23858), prompt injection, replay, formal analysis. | None specific; VI threat model and issue 29 |
| Openness and ecosystem | ||||||||
| Permissionless or registration required | Permissionless | Permissionless Anyone can run a facilitator; cloudflare:402 needs the signature agent registered with Cloudflare. | Registration required (Visa onboarding) | Registration required (bilateral onboarding) ChatGPT feeds limited to approved partners. | Permissionless; businesses may keep allowlists Google surfaces need Merchant Center onboarding. | Permissionless for chain methods; accounts for the stripe method Rails add methods without approval. | Open specification; verifiers choose which issuers or agent providers to trust No registration step defined. | Registration required (agents and merchants) |
| Decentralization | Open registries on public chains, with one upgrade key on Ethereum and Base | Open and permissionless, concentrated in practice Most payments go through one facilitator. | Centralized: one Visa-controlled key store | Centralized per platform Each agent platform onboards merchants; founders control governance. | Federated by domain, governance concentrated at Google Google holds proxy votes and the domain. | Open spec, concentrated authorship Five core authors from two companies; Tempo validators are permissioned; 126 of 129 listings accept Tempo. | Bilateral trust between parties; governed by an alliance No central operator in the protocol. | Centralized in Mastercard |
| Builds on (standards) | ERC-721 (URIStorage), EIP-712, ERC-1271, EIP-155, UUPS proxies | HTTP 402, EIP-712, EIP-3009, Permit2, ERC-7710, CAIP-2, CAIP-122, RFC 9421, BOLT11 Plus ERC-8021 builder codes. | RFC 9421, JWT, JWS, OpenID Connect ID Token, JWKS | REST, JSON Schema, OpenAPI, OpenRPC, EMV 3DS2, network tokens, HMAC-SHA256, RFC 8615, MCP, CommonMark No VCs, DIDs, RFC 9421 or chains. | RFC 9421, 9530, 8941, 7517, OAuth 2.0 family, JSON Schema, OpenAPI, OpenRPC, MCP, A2A | HTTP 402 auth (RFC 9110), JCS, RFC 9530, RFC 9457, HMAC, EIP-712, JWE, DID Plus OpenAPI and JSON-RPC for extensions. | SD-JWT (RFC 9901), SD-JWT VC, Delegate SD-JWT draft, RFC 7800, OpenID4VP, Digital Credentials API VC 2.0 and DIDs only as the wider family. | Network tokenization, RFC 9421, FIDO passkeys, SD-JWT, RFC 7800 |
| Composes with | x402 (x402Support, agentWallet, proofOfPayment); MPP discovery draft cites it; AP2 indirectly via A2A | AP2 (a2a-x402), ERC-8004, Stripe MPP, Visa TAP No link found with OpenAI ACP or UCP. | Stripe MPP, x402 (browsingIOU), OpenAI ACP and UCP via Intelligent Commerce Connect No documented link to AP2 or ERC-8004. | Stripe SPT; Visa and Mastercard agent tokens under SPTs; UCP side by side No documented link to x402, ERC-8004, TAP or AP2. | AP2 (extension); MCP and A2A (transports); network tokens via credential type | x402, Stripe SPT (ACP), Visa TAP and VIC, Mastercard AP4M (Tempo's statement) AP2 complementary with no cross-reference; no UCP or ERC-8004 link. | UCP (extension), x402 (a2a-x402, v0.1 target), Mastercard Verifiable Intent No documented link with TAP, ACP, MPP or ERC-8004. | AP2 and UCP via VI, ACP via Stripe SPT, MPP (Tempo statement), x402 (member) |
| Reference implementations and SDKs | erc-8004-contracts 2.0.0; agent0-sdk 1.7.1 (npm, PyPI); create-8004-agent; ChaosChain; Lucid Agents | @x402 TypeScript 2.28.0, PyPI x402 2.25.0, Go module v2 Java in the repository but unpublished; legacy V1 npm packages still downloaded. | visa/trusted-agent-protocol sample (unpackaged); mppx TAP attestation No Visa TAP package on npm or PyPI. | No official SDK; OpenAI and Stripe hosted services Svix publishes unofficial types; package.json name not on npm. | ucp-sdk (PyPI), @ucp-js/sdk (npm), ucp-schema (crates), samples, conformance | mppx 0.13.4 (TypeScript), pympp, Rust mpp, mpp-go, mpp-rb, Visa mpp-card Community SDKs in Elixir, Go and Swift. | Python SDK and samples in Python, Go and Android SDK not on PyPI; TypeScript SDK PR closed unmerged. | VI Python reference SDK; no Agent Pay SDK The Agent Toolkit is documentation only. |
| Economics and adoption | ||||||||
| Observability score | 5 of 5 All state and events are public; quality of the data is the weak point. | 3 of 5 Public settlements and endpoints, but payments look like ordinary transfers and headers stay private. | 1 of 5 Public JWKS and repository; no events, logs or counts. | 1 of 5 Only discovery documents and the GitHub repository are public. | 2 of 5 Public profiles and governance; transactions private. | 3 of 5 Public chain settlement and MPPscan; credentials, Stripe and card payments private. | 1 of 5 Everything except UCP profiles and GitHub activity is private. | 1 of 5 Nothing public beyond releases and the VI repository. |
| Fees and who pays them | No protocol fee; gas only Measured 2026-10-11 with eth_estimateGas: register about 203,412 gas, first giveFeedback about 155,185 to 178,504 gas; cents on mainnet that day, dollars at early-2026 gas prices. | No protocol fee; facilitator fee plus gas CDP: 1,000 free on-chain transactions a month, then $0.001 each; verification free (as of 2026-10-11). The facilitator pays gas on the EVM exact path and as Solana fee payer. | No TAP fee stated; VIC production fees on request; no agent-specific interchange published Evidence of absence from Visa pages and secondary reviews (2026). | No protocol fee; OpenAI charges merchants "a small fee" (rate unpublished); a 4 percent Shopify figure is reported only Merchant PSP fees unchanged; SPT pricing not published (public preview). | No protocol fee; Google says no cut (reported); merchant pays its PSP Google, Microsoft checkouts reported with no additional fee for now. | No protocol fee; rail fees Tempo gas at most about 0.0006 USD per 50,000-gas transfer, paid by the client unless the server sponsors; Stripe minimums 0.50 USD (cards) and 0.01 USDC; Stripe stablecoin fee reported, not confirmed for MPP; SPT pricing not published (as of 2026-10-11). | No protocol fee Costs are those of the underlying rail. | Not published; card economics unchanged No price table, interchange category, token fee or liability rule published. |
| Who pays (short) | Caller pays gas Owner pays to register; client or an EIP-7702 sponsor pays for feedback. | Facilitator pays gas; seller pays the facilitator fee On Solana the merchant can sponsor as fee payer; cloudflare:402 is billed by Cloudflare. | Card economics unchanged Merchant pays usual acquiring fees. | Merchant pays platform fee Card economics otherwise unchanged. | Merchant pays PSP only | Client pays gas unless the server sponsors; card economics unchanged Server always pays settle and close; Stripe can pay Tempo fees with hostedFeePayer. | Card or rail economics unchanged AP2 adds no fee; merchants may carry a second signing key type. | Card economics unchanged Merchant pays its usual card acceptance fees. |
| Adoption evidence | Many registrations, few live agents 561,576+ agents on 8004scan (2026-10-11) against 3% to 15% live in arXiv:2606.26028 (data to 2026-05-13). Count is not quality. | Real but contested x402.org showed $24.24M over 30 days (last updated 2026-08-25); Visa and Artemis adjusted cumulative activity to about $15.0M across 109.6M transactions (data to 2026-04-21). | Four merchants named live (2026-07-02); Cloudflare and Akamai at the edge No count of verifying merchants published. | Named partners, no volume data Seven retailers for discovery; Copilot, PayPal, Walmart announcements; no GMV published. | Live Google checkout (Etsy, Wayfair); 21 co-developers, 51 endorsers; no merchant counts AP2 inside UCP: unverified. | Live but small and mostly Tempo MPPscan: 4,072,426 transactions and 435,476 USD all time, 8,774 USD in the last 30 days (2026-10-11); 129 directory services. | Unverified anywhere, including inside UCP One self-reported deployment (issue 345); 3,216 GitHub stars on 2026-10-11. | Named pilots; no volume data |
| Policy and outlook | ||||||||
| Regulatory touchpoints | Data protection (permanent public records); no KYC; payment rules apply to linked rails | Stablecoin, money transmission and sanctions rules fall on facilitators and sellers No KYC or sanctions layer in the protocol; the CDP facilitator runs OFAC and KYT checks. | Card liability rules (Reg Z and E, PSD2, UK PSRs), SCA, GDPR for consumer data | Card rules, PCI DSS, SCA via 3DS, consumer protection; AI transparency on the surface Merchant of record keeps tax and compliance. | Card law (Reg Z, Reg E, PSD2 SCA), GDPR, AI Act Article 50 Merchant's PSP handles SCA and disputes. | Card law for card methods; stablecoin, AML and sanctions rules for chain methods No KYC or sanctions layer in the core. | Consent and unauthorized-transaction rules; SCA Regulation E and Z, PSD2 and UK PSRs; no compliance claim in the spec. | Regulation Z and E, PSD2 SCA, UK PSRs, network rules, EMVCo |
| Biggest open question | Can reputation be made Sybil-resistant without a gate, and who controls the upgrade key? | How much activity is real commerce, and can payment and delivery be made atomic? | How do production agent keys reach verifiers, and will TAP converge with Web Bot Auth? | Does ACP checkout survive beyond feeds, and who besides ChatGPT runs it in production? | Will checkout spread beyond Google surfaces and will AP2 mandates go live? | Will it become a real standard with a neutral home, and is the traffic real commerce? | Will FIDO publish it and will anyone deploy it? No FIDO deliverable and no verified production use as of 2026-10-11. | Liability for agent purchases within limits |
Pick two
Choose two protocols. Rows whose values differ are marked. The comparison is textual, so “same” means the same wording, not a judgment that the designs are equivalent.
33 dimensions differ, 1 read the same, 0 have an entry on one side only. Values are compared as text, so read the details before you draw a conclusion.
| Dimension | Status | ERC-8004 | x402 |
|---|---|---|---|
| Primary job | Differs | On-chain agent identity, discovery and public feedback Three registries: identity (ERC-721 plus a registration file), reputation, and validation (specified only). | Pay-per-request payments over HTTP 402 The server prices a request in a 402 response, the client signs a payment, a facilitator verifies and settles it. |
| Layers covered | Differs | Identity and trust; reputation and feedback; discovery No checkout, authorization or settlement layer. | Settlement rails and payment credential; discovery through Bazaar; refunds only in auth-capture No identity, intent or checkout layer. |
| Stewards | Differs | ERC-8004 team (community), coordinated by De Rossi (MetaMask) and Crapis (Ethereum Foundation) Co-authors Jordan Ellis (Google) and Erik Reppel (Coinbase); no foundation found. | x402 Foundation (Linux Foundation); TSC: Coinbase, Cloudflare, Stripe Originated at Coinbase Developer Platform. |
| Governance model | Differs | ethereum/ERCs editorial process; contracts controlled by one proxy owner An EIP editor returned the text to Draft on 2026-01-13; one externally owned account owns the proxies on Ethereum and Base (2026-10-11). | Foundation under an LF Projects technical charter TSC with one vote per representative and majority decisions; 75 percent supermajority for Core Principles. |
| License (spec and code) | Differs | Spec CC0; contracts MIT per file headers (README says CC0) | Apache-2.0 No separate docs license found; contributions need GPG-signed commits. |
| First announced | Differs | 2025-08-13 (created) Merged into ethereum/ERCs on 2025-08-18. | 2025-05-06 Whitepaper and npm launch. |
| Latest version and date | Differs | Draft text of 2026-01-25; contracts 2.0.0 | Spec v2.0 (2025-12-09); @x402/core 2.28.0 (2026-09-29) V2 launched 2025-12-11. |
| Maturity | Differs | Draft ERC; Identity and Reputation live on 25 mainnets; Validation not officially deployed README list as of 2026-08-15, unchanged on 2026-10-11. | Live (V2 since 2025-12-11) upto, batch-settlement, auth-capture and Lightning are 2026 additions with uneven SDK coverage. |
| Transports | Differs | EVM transactions and reads; files over IPFS, HTTPS or data URI; /.well-known domain proof | HTTP headers, MCP _meta, A2A task metadata The facilitator API is HTTP in every case. |
| Settlement rails | Differs | None (moves no money) Registries live on EVM chains; payments happen on other rails. | EVM chains, Solana, Lightning and other CAIP-2 networks; credit-backed cloudflare:402 Fiat ids such as ach:us appear only as examples of the id format. |
| Agent identity model | Differs | ERC-721 token per agent pointing to a registration file; global id agentRegistry plus agentId | None in the core; optional extensions sign-in-with-x (CAIP-122), auth-hints (OAuth 2.0 with DPoP), RFC 9421 agent signatures in cloudflare:402. |
| User authorization model | Differs | None No consent or mandate object; ERC-8226 (Draft) proposes one on top. | The client signature on each payment No user mandate object; AP2 mandates can carry x402 through a2a-x402. |
| Human-present and human-not-present support | Differs | Not applicable Registries record identity and feedback, not purchases. | Both Built for unattended clients with SDK spend controls; @x402/paywall serves humans; AP2 ships human-present and human-not-present x402 samples. |
| Merchant of record | Differs | Not applicable No payment flows through ERC-8004. | The resource server In cloudflare:402 the network (Cloudflare) is merchant of record. |
| Credential type | Differs | ERC-721 token plus EIP-712 or ERC-1271 wallet-binding signature | Signed payment authorization EIP-3009 or Permit2 signatures, ERC-7710 delegations, a partially signed Solana transaction, or a Lightning preimage. |
| Cryptography | Differs | EIP-712, ERC-1271, keccak256 file commitments ECDSA recovery also accepts EIP-7702 delegated accounts in the reference code. | EIP-712 typed-data signatures; Ed25519 for RFC 9421 and Solana; SHA-256 preimages on Lightning Smart wallets through ERC-1271 and ERC-6492. |
| Replay protection | Differs | Partial: EIP-712 domain and a 5-minute deadline on wallet binding, no nonce | Single-use nonce plus a validity window, enforced by the token contract Replay stores for Lightning payment hashes; cumulative vouchers in batch-settlement. |
| Native spending controls | Differs | None (moves no money) | None in the protocol; SDK default of $1 per payment Budgets are out of scope in the spec; upto signs a ceiling. |
| Revocation | Differs | Feedback revocation by its client; wallet unset; no identity revocation or burn | None for a signed exact payment before it expires auth-capture adds void and client reclaim; channels allow timed withdrawal. |
| Refunds and disputes | Differs | No disputes; appendResponse can show a refund | No refunds in exact; no dispute process auth-capture refunds; third-party x402r for refunds and arbitration. |
| Privacy exposure | Differs | Everything on-chain is public and permanent; files public if their URI is The text says on-chain pointers and hashes cannot be deleted. | Settlements are public on chain; resource metadata reaches the facilitator Header contents stay private between client, server and facilitator. |
| Discovery mechanism | Differs | Registration files with services (A2A, MCP, web, ENS, DID), indexed by explorers and subgraphs | Bazaar extension and GET /discovery/resources Public CDP Bazaar; x402scan reads /openapi.json and /.well-known/x402. |
| Permissionless or registration required | Same | Permissionless | Permissionless Anyone can run a facilitator; cloudflare:402 needs the signature agent registered with Cloudflare. |
| Decentralization | Differs | Open registries on public chains, with one upgrade key on Ethereum and Base | Open and permissionless, concentrated in practice Most payments go through one facilitator. |
| Observability score | Differs | 5 of 5 All state and events are public; quality of the data is the weak point. | 3 of 5 Public settlements and endpoints, but payments look like ordinary transfers and headers stay private. |
| Fees and who pays them | Differs | No protocol fee; gas only Measured 2026-10-11 with eth_estimateGas: register about 203,412 gas, first giveFeedback about 155,185 to 178,504 gas; cents on mainnet that day, dollars at early-2026 gas prices. | No protocol fee; facilitator fee plus gas CDP: 1,000 free on-chain transactions a month, then $0.001 each; verification free (as of 2026-10-11). The facilitator pays gas on the EVM exact path and as Solana fee payer. |
| Who pays (short) | Differs | Caller pays gas Owner pays to register; client or an EIP-7702 sponsor pays for feedback. | Facilitator pays gas; seller pays the facilitator fee On Solana the merchant can sponsor as fee payer; cloudflare:402 is billed by Cloudflare. |
| Builds on (standards) | Differs | ERC-721 (URIStorage), EIP-712, ERC-1271, EIP-155, UUPS proxies | HTTP 402, EIP-712, EIP-3009, Permit2, ERC-7710, CAIP-2, CAIP-122, RFC 9421, BOLT11 Plus ERC-8021 builder codes. |
| Composes with | Differs | x402 (x402Support, agentWallet, proofOfPayment); MPP discovery draft cites it; AP2 indirectly via A2A | AP2 (a2a-x402), ERC-8004, Stripe MPP, Visa TAP No link found with OpenAI ACP or UCP. |
| Reference implementations and SDKs | Differs | erc-8004-contracts 2.0.0; agent0-sdk 1.7.1 (npm, PyPI); create-8004-agent; ChaosChain; Lucid Agents | @x402 TypeScript 2.28.0, PyPI x402 2.25.0, Go module v2 Java in the repository but unpublished; legacy V1 npm packages still downloaded. |
| Adoption evidence | Differs | Many registrations, few live agents 561,576+ agents on 8004scan (2026-10-11) against 3% to 15% live in arXiv:2606.26028 (data to 2026-05-13). Count is not quality. | Real but contested x402.org showed $24.24M over 30 days (last updated 2026-08-25); Visa and Artemis adjusted cumulative activity to about $15.0M across 109.6M transactions (data to 2026-04-21). |
| Published security research | Differs | Yes: an empirical study of Sybil reviewers and liveness; an unmerged community audit; no CVE | Yes: several 2026 papers and two high-severity advisories Five attacks, free-riding flaws, facilitator risks, A402, PII leakage, formal analysis; GHSA-3j63-5h8p-gf7c and GHSA-qr2g-p6q7-w82m. |
| Regulatory touchpoints | Differs | Data protection (permanent public records); no KYC; payment rules apply to linked rails | Stablecoin, money transmission and sanctions rules fall on facilitators and sellers No KYC or sanctions layer in the protocol; the CDP facilitator runs OFAC and KYT checks. |
| Biggest open question | Differs | Can reputation be made Sybil-resistant without a gate, and who controls the upgrade key? | How much activity is real commerce, and can payment and delivery be made atomic? |
Radar
Six axes scored 0 to 5: openness, decentralization, maturity, adoption evidence, human-not-present support, dispute support. Scores are editorial judgments made from the cited sources, not measurements. Hover or focus a point to read its justification; the table below has the same values with citations.
ERC-8004
x402
Visa TAP
OpenAI ACP
UCP
Stripe MPP
AP2
Mastercard Agent Pay
| Protocol | Openness | Decentralization | Maturity | Adoption evidence | Human-not-present support | Dispute support |
|---|---|---|---|---|---|---|
| ERC-8004 | 5 of 5 CC0 text, open contracts, permissionless registration on public chains. Source [1, 2] | 3 of 5 Public chains and anyone can read or write, but one externally owned account can upgrade the registries on Ethereum and Base. Source [1, 4] | 2 of 5 Draft ERC with two of three registries deployed; the text last changed 2026-01-25. Source [2, 8] | 2 of 5 Hundreds of thousands of registrations but only 3% to 15% live agents and majority Sybil reviewers in measured data. Source [12, 21] | 4 of 5 Designed for agents to find and rate agents without people; no payment or consent step to support. Source [1] | 1 of 5 Only appendResponse and feedback revocation; no dispute process. Source [1] |
| x402 | 5 of 5 Apache-2.0 code and specs in a public repository, governed by a Linux Foundation project; anyone can implement or run a facilitator. Source [33, 34, 60] | 3 of 5 Permissionless facilitation and many networks, but one facilitator carries most volume and three companies form the TSC. Source [31, 62, 63] | 4 of 5 V2 live since 2025-12-11 with frequent SDK releases and three contract audits; several schemes are 2026 additions. Source [27, 37, 38] | 3 of 5 Measurable on-chain activity and live products, but volume figures are contested and partly manufactured. Source [74, 75, 274] | 4 of 5 Designed for unattended clients that pay per request with SDK spend controls; no user mandate object of its own. Source [26, 49] | 1 of 5 No dispute process and no refund in exact; auth-capture adds refunds and reclaim. Source [29, 55] |
| Visa TAP | 1 of 5 Public specification but revocable proprietary terms that forbid modification. Source [84] | 1 of 5 One Visa-controlled key store and Visa onboarding of agents. Source [69, 89] | 2 of 5 Unversioned specification, no test vectors, sample unchanged since 2025-10-28. Source [69, 86] | 2 of 5 Named live merchants and CDNs, no counts of verifying merchants. Source [87, 100] | 2 of 5 Signs agent requests without the user present; consent and limits come from VIC. Source [69, 83] | 2 of 5 No dispute mechanism in TAP; card rules and VIC signals apply. Source [83, 91] |
| OpenAI ACP | 3 of 5 Apache-2.0 spec in a public repository with a CLA, but the founders appoint the TSC and keep a veto. Source [109, 111] | 1 of 5 Bilateral onboarding per platform and founder-controlled governance; no permissionless path. Source [106, 109] | 2 of 5 Beta and Draft labels, mutable releases, examples that do not validate, and a quiet repository since 2026-07-18. Source [115, 116] | 2 of 5 Large named partners for feeds, but no published volume and a scaled-back checkout product. Source [113, 117] | 1 of 5 Built around a buyer confirming in session; tokens are one-time and session bound. Source [113, 121] | 2 of 5 Merchant handles chargebacks under card rules and reports adjustments; no dispute protocol. Source [126, 128] |
| UCP | 4 of 5 Apache-2.0 spec and SDKs, public repository and Discussions; governance favors Google. Source [145, 147] | 2 of 5 Any domain can publish a profile, but Google holds proxy votes until December 2028 and the domain, and one platform dominates live use. Source [145, 152] | 3 of 5 Four dated releases and a live Google deployment; frequent breaking changes and drafts on main. Source [150, 275] | 3 of 5 Live US checkout on Google surfaces and many endorsers, but no merchant or volume figures. Source [152, 164] | 1 of 5 Buyer places the order in a trusted UI unless the AP2 extension is active, and AP2 live use is unverified. Source [143, 144] | 2 of 5 Order adjustments record disputes and refunds; resolution stays with merchant and card rules. Source [161] |
| Stripe MPP | 4 of 5 CC0 specs, permissionless methods and open SDKs, but no neutral governance body. Source [178, 180] | 2 of 5 Authorship from two companies, a permissioned Tempo validator set, and nearly all listed services on Tempo. Source [175, 200, 201] | 3 of 5 Live since 2026-03-18 with several SDKs, but the core is an individual draft and Stripe's integration is labeled Frontier. Source [179, 186] | 2 of 5 Millions of indexed transactions but under one cent each recently, and few non-Tempo listings. Source [200, 202] | 4 of 5 Designed for unattended clients with deposit-capped sessions and access-key subscriptions; no user mandate object. Source [192, 194] | 2 of 5 Chargebacks only on card routes; none on stablecoin routes. Source [197, 198] |
| AP2 | 4 of 5 Apache-2.0 specification and schemas in public; specification work now in FIDO, whose drafts are member-only. Source [98, 216] | 3 of 5 No central operator; each verifier chooses whom to trust; governance by an industry alliance. Source [216, 225] | 2 of 5 v0.2 specification with schemas and samples; spec contradictions open and no public FIDO draft. Source [220, 232] | 1 of 5 Named collaborators and a UCP extension, but no verified production use. Source [217, 219, 237] | 5 of 5 Open mandates with constraints and agent keys were designed for this case. Source [226, 229] | 3 of 5 Defined dispute verification over mandates and receipts; retention and adjudication left out. Source [214] |
| Mastercard Agent Pay | 1 of 5 Proprietary program with an unpublished Acceptance Framework; only Verifiable Intent is open. Source [248, 249] | 0 of 5 Mastercard alone registers agents, runs the directory and issues tokens. Source [244] | 2 of 5 Network enablement in several regions but named transactions are pilots; developer docs an early preview. Source [252, 276] | 2 of 5 Many named banks and partners, no volume data. Source [251, 252, 254] | 3 of 5 Tokens with limits and VI Autonomous mandates support delegation; VI not shown in live authorizations. Source [245, 255] | 2 of 5 Card chargeback rights apply; no agent-specific codes; VI evidence without liability rules. Source [245, 258] |
How to read this page
Each protocol writer fills its own column from the protocol's claims and sources, and a separate reviewer reads the matrix for overclaims. Confidence follows the site rule: verified means a primary source was read, reported means reputable secondary sources only, unverified is shown with a badge. See the methodology for counts and gaps, the controls map for control-by-control support and the stack for layers.
Sources
- ERC-8004: Trustless Agents (specification source, ERCS/erc-8004.md) (external link)
- erc-8004-contracts README (external link)
- Update erc-8004.md (#1470) (external link)
- On-chain reads of the ERC-8004 proxies (owner, getVersion, ERC-1967 implementation slot) on Ethereum and Base (external link)
- IdentityRegistryUpgradeable.sol (external link)
- Add ERC: Trustless Agents (#1170) (external link)
- Update ERC-8004: Updates from community feedback (external link)
- ERC-8004: Trustless Agents (external link)
- ReputationRegistryUpgradeable.sol (external link)
- ERC-8226: Regulated Agent Mandate (external link)
- Agent0 subgraphs live: indexing the ERC-8004 agent economy (external link)
- 8004scan: ERC-8004 agent explorer (home page statistics) (external link)
- ERC-8004 Explorer FAQ (external link)
- Gas estimates for register and giveFeedback via eth_estimateGas on Ethereum and Base (external link)
- ERC-8004: On-chain identity standard for AI agents (external link)
- draft-payment-discovery-01 (MPP payment discovery extension) (external link)
- AP2 Glossary (external link)
- agent0-sdk (npm) (external link)
- agent0-sdk (PyPI) (external link)
- create-8004-agent (npm) (external link)
- Can Trustless Agents Be Trusted? An Empirical Study of the ERC-8004 Decentralized AI Agent Ecosystem (external link)
- ERC-8004 agent census (measured read, 2026-09-26) (external link)
- Security Audit: Fix response downgrade vulnerability + comprehensive report (PR 51) (external link)
- Commit history of erc-8004/erc-8004-contracts (external link)
- Regulation (EU) 2016/679 (General Data Protection Regulation) (external link)
- x402 Protocol Specification v2 (external link)
- x402 repository (README, specs, SDKs, contracts) (external link)
- Extension: bazaar (external link)
- Scheme: auth-capture (external link)
- Linux Foundation Announces Operational Launch of x402 Foundation (external link)
- TSC.md (Technical Steering Committee roster) (external link)
- x402: An open standard for internet-native payments (whitepaper) (external link)
- Technical Charter for x402 a Series of LF Projects, LLC (external link)
- x402 LICENSE (Apache License 2.0) and NOTICE (external link)
- x402 CONTRIBUTING.md (external link)
- x402 (legacy V1 TypeScript package) on npm (external link)
- @x402/core on npm (external link)
- x402 PR #705: Development v2 (external link)
- x402 docs: SDK features and parity (external link)
- x402 HTTP transport (V2) (external link)
- x402 MCP transport (V2) (external link)
- x402 A2A transport (V2) (external link)
- x402 docs: Network and token support (external link)
- Scheme: batch-settlement on cloudflare:402 (external link)
- Extension: sign-in-with-x (external link)
- Extension: auth-hints (external link)
- Scheme: exact on EVM (external link)
- A2A x402 extension specification v0.2 (external link)
- x402Client.ts (SpendControls, DEFAULT_MAX_AMOUNT_PER_PAYMENT) (external link)
- AP2 repository x402 samples (external link)
- Scheme: exact on Solana (SVM) (external link)
- Scheme: exact on Lightning (lnbtc) (external link)
- @x402/core CHANGELOG.md (external link)
- Scheme: batch-settlement on EVM (external link)
- Scheme: exact (network independent) (external link)
- x402 docs: third-party SDKs and extensions (external link)
- Hardening x402: PII-Safe Agentic Payments via Pre-Execution Metadata Filtering (external link)
- CDP Bazaar discovery (external link)
- x402scan docs/DISCOVERY.md (external link)
- x402 docs: Facilitator (external link)
- Extension: http-message-signatures (external link)
- CDP x402 docs: Welcome (external link)
- When HTTP 402 Meets the Blockchain: Risks on Emerging x402 Payments (external link)
- ERC-8004 best practices: Reputation (external link)
- x402scan repository (external link)
- CDP x402 facilitator: pricing and supported networks (external link)
- ERC-8004: Trustless Agents (external link)
- MPP vs x402 (external link)
- Trusted Agent Protocol merchant specifications (external link)
- x402 on PyPI (external link)
- Go SDK changelog fragment v2.28.0 (external link)
- Java SDK pom.xml (1.0.0-SNAPSHOT) (external link)
- x402.org (site and Last 30 Days counters) (external link)
- Visa/Artemis: The $0.14 Reality of Agent Commerce (external link)
- How Agentic Is Agentic Commerce? A Population-Scale Measurement of x402 Adoption and Authenticity (external link)
- Five Attacks on x402 Agentic Payment Protocol (external link)
- Free-Riding the Agentic Web: A Systematic Security Analysis of x402 Payments (external link)
- GHSA-3j63-5h8p-gf7c: x402 legacy npm packages below 0.5.2 (external link)
- GHSA-qr2g-p6q7-w82m: facilitators processing Solana payments (external link)
- CDP x402 facilitator docs (pricing, networks, KYT and OFAC) (external link)
- A402: Binding Cryptocurrency Payments to Service Execution for Agentic Commerce (external link)
- Visa Introduces Trusted Agent Protocol: An Ecosystem-Led Framework for AI Commerce (external link)
- Visa Intelligent Commerce overview (Visa Developer Center) (external link)
- Trusted Agent Protocol Product Terms (external link)
- Trusted Agent Protocol repository LICENSE.md (external link)
- visa/trusted-agent-protocol repository metadata, commits, pull requests and issues (GitHub API) (external link)
- Visa and Banks Across Europe Reach the Next Phase of Agentic Commerce, Unlocking Secure Access to Merchants (external link)
- Trusted Agent Protocol overview (Visa Developer Center) (external link)
- Visa well-known JWKS (live fetch) (external link)
- RFC 9421: HTTP Message Signatures (external link)
- Agentic commerce liability is still being written (external link)
- Visa Announces New AI, Stablecoin and Token Innovations to Power Intelligent, Programmable Commerce at Visa Payments Forum (external link)
- Securing agentic commerce: helping AI Agents transact with Visa and Mastercard (external link)
- Visa Intelligent Commerce Review (external link)
- Merchant Cost Consulting article on agentic commerce fees (external link)
- draft-card-charge-00: Card Network Charge Intent for HTTP Payment Authentication (external link)
- Visa Opens the Door to AI-Driven Shopping for Businesses Worldwide (Intelligent Commerce Connect) (external link)
- AP2 repository (README, METADATA, LICENSE) at e1ea56d (external link)
- mppx TAP attestation constants (src/tap/Constants.ts) (external link)
- Akamai and Visa join forces to secure the next era of agentic commerce (external link)
- RAILS: Verification-Native Clearing For Agentic Commerce (external link)
- A Formal Analysis of Agent Payment Protocols (arXiv 2609.00060) (external link)
- 12 CFR 1026.12 Special credit card provisions (Regulation Z), paragraph (b) liability of cardholder for unauthorized use (external link)
- Commission Delegated Regulation (EU) 2018/389 (RTS on strong customer authentication and common and secure communication) (external link)
- draft-ietf-webbotauth-httpsig-protocol-00: HTTP Message Signatures for automated traffic (external link)
- RFC: Agentic Checkout, Merchant REST API (external link)
- RFC: Agentic Commerce, Delegate Payment (external link)
- ACP changelog, version 2026-04-17 (external link)
- Agentic Commerce Protocol (ACP) Governance (external link)
- ACP MAINTAINERS.md (external link)
- ACP LICENSE (Apache License 2.0) and NOTICE (external link)
- ACP CLA Signatories (external link)
- Buy it in ChatGPT: Instant Checkout and the Agentic Commerce Protocol (external link)
- Stripe powers Instant Checkout in ChatGPT and releases Agentic Commerce Protocol co-developed with OpenAI (external link)
- GitHub commits API for agentic-commerce-protocol/agentic-commerce-protocol (per-path history) (external link)
- Agentic Commerce Protocol (ACP) README (external link)
- Powering Product Discovery in ChatGPT (external link)
- Monetization (Apps SDK): external checkout and ChatGPT payment sheet (external link)
- MCP Transport Binding for Agentic Checkout (external link)
- ACP OpenAPI, Feed API, 2026-04-17 (external link)
- ACP JSON Schema, Delegate Payment, 2026-04-17 (external link)
- RFC: Seller-Backed Payment Handler (external link)
- Shared payment tokens (Stripe Docs; seller and agent variants) (external link)
- ACP OpenAPI, Delegate Payment, 2026-04-17 (external link)
- ACP rfcs directory (status lines of all 15 RFCs) (external link)
- Agentic Commerce (OpenAI developer documentation; full Markdown export at /commerce/llms-full.txt) (external link)
- ACP OpenAPI, Agentic Checkout Webhooks, 2026-04-17 (external link)
- ACP JSON Schema, Agentic Checkout, 2026-04-17 (external link)
- RFC: Agentic Checkout, Discovery (external link)
- Agentic Commerce Protocol website (external link)
- Shopify Merchants to Pay 4% Fee on ChatGPT Checkout Sales (external link)
- Agentic commerce (Stripe Docs) (external link)
- agentic-commerce-protocol on npm and PyPI (Svix type definitions, 0.2.0) (external link)
- npm registry lookup for @agentic-commerce-protocol/specification (HTTP 404) (external link)
- Conversations that Convert: Copilot Checkout and Brand Agents (external link)
- OpenAI and PayPal Team Up to Power Instant Checkout and Agentic Commerce in ChatGPT (external link)
- A Formal Analysis of Agent Payment Protocols (external link)
- GitHub security advisories for the ACP repository (API returned 0) (external link)
- Building Trust in Autonomous Commerce: A Verifiable Global Event Timeline and AI-Ready Fraud Intelligence Layer (external link)
- Regulation (EU) 2026/1744 (Digital Omnibus on AI), OJ L 2026/1744 of 24.7.2026 (external link)
- Agentic Commerce (Microsoft Advertising solutions page) (external link)
- UCP Official Specification overview (v2026-08-25) (external link)
- Checkout Capability (v2026-08-25) (external link)
- AP2 Mandates Extension (v2026-08-25) (external link)
- UCP GOVERNANCE.md (external link)
- UCP MAINTAINERS.md (external link)
- GitHub repository metadata for Universal-Commerce-Protocol/ucp (external link)
- The next era of agentic retail (NRF 2026 remarks) (external link)
- Under the Hood: Universal Commerce Protocol (UCP) (external link)
- UCP GitHub releases and tags (external link)
- UCP JavaScript SDK README (external link)
- What to expect in digital advertising and commerce in 2026 (external link)
- Payment type schemas (v2026-08-25) (external link)
- Frequently Asked Questions, Google UCP Guide (external link)
- UCP Message Signatures (v2026-08-25) (external link)
- Identity Linking Capability (v2026-08-25) (external link)
- Google Shopping introduces Universal Cart (external link)
- UCP glossary (v2026-08-25) (external link)
- Agentic commerce and Copilot Checkout (external link)
- checkout.json schema (v2026-08-25) (external link)
- order.json, fulfillment_event.json, adjustment.json schemas (v2026-08-25) (external link)
- US Senator Demands Answers on Google's New Commerce Protocol (external link)
- Google Universal Commerce Protocol (UCP) Guide (external link)
- Universal Commerce Protocol (UCP) home page (external link)
- Google Gemini agentic shopping protocol (The Register) (external link)
- Shopify Merchants to Pay 4% Fee on ChatGPT Checkout Sales (external link)
- ucp-sdk on PyPI (external link)
- @ucp-js/sdk on npm (external link)
- ucp-schema on crates.io (external link)
- UCP samples repository (external link)
- Zero-Trust Runtime Verification for Agentic Payment Protocols: Mitigating Replay and Context-Binding Failures in AP2 (external link)
- Strabo: Declarative Specification and Implementation of Agentic Interaction Protocols (external link)
- GitHub security advisories for Universal-Commerce-Protocol repositories (external link)
- Regulation (EU) 2024/1689 (Artificial Intelligence Act) (external link)
- The "Payment" HTTP Authentication Scheme (draft-httpauth-payment-01, repository source) (external link)
- tempoxyz/mpp-specs repository (README, CONTRIBUTING, specs) (external link)
- Service Discovery for HTTP Payment Authentication (draft-payment-discovery-01) (external link)
- MPP governance page (external link)
- draft-httpauth-payment (IETF Datatracker record and history) (external link)
- mpp-specs LICENSE.md (external link)
- wevm/mppx repository (README, src, SECURITY.md) (external link)
- Introducing the Machine Payments Protocol (Stripe blog) (external link)
- tempoxyz/mpp-specs commit history (GitHub API) (external link)
- mppx on npm (external link)
- Tempo Mainnet is live (Tempo blog) (external link)
- Stripe docs: MPP (Machine Payments Protocol) (external link)
- IANA HTTP Authentication Scheme Registry and HTTP Field Name Registry (external link)
- Payment Authentication Scheme: JSON-RPC and MCP Transport (draft-payment-transport-mcp-00) (external link)
- Payment methods overview (mpp.dev) (external link)
- Expanding identity support in mppx (MPP blog) (external link)
- Card Network Charge Intent for HTTP Payment Authentication (draft-card-charge-00) (external link)
- Tempo Session Intent for HTTP Payment Authentication (draft-tempo-session-00) (external link)
- Stripe Charge Intent for HTTP Payment Authentication (draft-stripe-charge-00) (external link)
- Tempo Subscription Intent for HTTP Payment Authentication (draft-tempo-subscription-00) (external link)
- Tempo Charge Intent for HTTP Payment Authentication (draft-tempo-charge-00) (external link)
- Subscription Intent for HTTP Payment Authentication (draft-payment-intent-subscription-00) (external link)
- Charge Intent for HTTP Payment Authentication (draft-payment-intent-charge-00) (external link)
- Stripe docs: Stablecoin payments (external link)
- Tempo docs: Connection details (external link)
- MPP payments directory API (mpp.dev/api/services) (external link)
- Tempo docs: Consensus and finality (Simplex BFT) (external link)
- MPPscan, the Machine Payments Protocol Explorer (site and stats API) (external link)
- Tempo docs: Fees (external link)
- MPP vs x402: Agentic payment protocols compared (external link)
- Visa introduces card specification and SDK for Machine Payments Protocol (external link)
- Mastercard Launches Agent Pay for Machines to Unlock Super-Fast, Always-On Payments (external link)
- UCP repository (searched for MPP references) (external link)
- MPP SDK registry records (npm mpp-card, @solana/mpp, @stellar/mpp, @monad-crypto/mpp; PyPI pympp; crates.io mpp; RubyGems mpp-rb; Go proxy mpp-go) (external link)
- SDKs and client libraries (mpp.dev) (external link)
- A Formal Analysis of Agent Payment Protocols (external link)
- wevm/mppx repository security advisories (external link)
- GHSA-fxc9-7j2w-vx54: mpp (Rust) multiple payment bypass and griefing vulnerabilities (external link)
- Public Law 119-27, GENIUS Act (S. 1582) (external link)
- Agentic Payment Protocol (v0.2) specification (external link)
- AP2 Implementation Considerations (external link)
- FIDO Alliance to Develop Standards for Trusted AI Agent Interactions (external link)
- AP2 FAQ (external link)
- FIDO Alliance Launches Payments Working Group (external link)
- Powering AI commerce with the new Agent Payments Protocol (AP2) (external link)
- AP2 GitHub releases v0.1.0 and v0.2.0 (external link)
- AP2 commit history on main (GitHub commits API) (external link)
- Beyond the Mandate: A Systematic Security Analysis of the Agent Payments Protocol (AP2) (external link)
- UCP AP2 Mandates Extension (external link)
- AP2 JSON Schema shared types (amount, merchant, payment_instrument, pisp, item, jwk, receipt_status) (external link)
- AP2 Agent Authorization (external link)
- AP2 Flow Examples (external link)
- AP2 Security and Privacy Considerations (external link)
- Zero-Trust Runtime Verification for Agentic Payment Protocols: Mitigating Replay and Context-Binding Failures in AP2 (external link)
- AP2 JSON Schema: Open Payment Mandate (external link)
- AP2 JSON Schema: Open Checkout Mandate (external link)
- AP2 JSON Schema: Payment Mandate (external link)
- Issue 268: Checkout JWT algorithm constraint forces dual keys under WBA (and conflicts with normative Security and Privacy guidance) (external link)
- Delegate SD-JWT (draft-gco-oauth-delegate-sd-jwt-00) (external link)
- A2A Protocol: x402 Payments Extension v0.2 (external link)
- Verifiable Intent specification README (0.1-draft) (external link)
- AP2 issues and pull requests opened since 2026-04-29 (GitHub issues API) (external link)
- Issue 345: Merchant-side AP2 v0.2 implementation report: Suede Agent Studio (external link)
- GitHub API repository metadata for google-agentic-commerce/AP2 (external link)
- Whispers of Wealth: Red-Teaming Google's Agent Payments Protocol via Prompt Injection (external link)
- AP2 GitHub security advisories (empty) and NVD keyword search (external link)
- 12 CFR 1005.2 Definitions (Regulation E), paragraph (m) unauthorized electronic fund transfer (external link)
- Directive (EU) 2015/2366 (PSD2) (external link)
- Mastercard Unveils Agent Pay, Pioneering Agentic Payments Technology to Power Commerce in the Age of AI (external link)
- The Rails for Agentic Commerce (external link)
- Level 1 Agentic Commerce: Enable Agent Support with Minimal Changes (external link)
- Verifiable Intent (VI): Specification Overview, version 0.1-draft (external link)
- FIDO Alliance to Develop Standards for Trusted AI Agent Interactions (external link)
- Level 3 Agentic Commerce: Advanced Programmatic Checkout (external link)
- Verifiable Intent README (external link)
- BREAKING: Field alignment v2 (constraint prefixes, cnf restructure, risk_data, VCT versioning) (external link)
- Mastercard Advances Agentic Commerce With New Trust and Intelligence Services (external link)
- Europe is Building the Foundations for Trusted Agentic Commerce (external link)
- Santander and Mastercard complete Europe’s first live end-to-end payment executed by an AI agent (external link)
- Mastercard advances agentic payments in Latin America and the Caribbean with live transactions completed across the region (external link)
- Verifiable Intent: Credential Format Specification, version 0.1-draft (external link)
- Mastercard Virtual Card Tokens (external link)
- Verifiable Intent: Constraint Type Definitions and Validation Rules (external link)
- Verifiable Intent: Security Model and Threat Analysis, version 0.1-draft (external link)
- Mastercard Developers llms.txt service index (external link)
- Mastercard Agent Pay review (external link)
- Securing agentic commerce: helping AI Agents transact with Visa and Mastercard (external link)
- GitHub API: agent-intent/verifiable-intent repository metadata (external link)
- Merchant Cost Consulting note on agentic card fees (external link)
- RFC 9421: HTTP Message Signatures (external link)
- Verifiable Intent: Protocol Ecosystem (external link)
- Supporting additional payment methods for agentic commerce (external link)
- Linux Foundation Announces Operational Launch of x402 Foundation (external link)
- Verifiable Intent pyproject.toml (package verifiable-intent 0.1.0) (external link)
- Agent Toolkit API client (developer.mastercard.com llms.txt endpoints) (external link)
- Issuer-Sovereign Agentic Payments (external link)
- VI v0.1 L2 format lists each mandate disclosure digest in both _sd and delegate_payload; RFC 9901 requires verifiers to reject the credentials (external link)
- EMVCo Requests Feedback on Framework for Secure, Interoperable and Scalable Card-Based Agentic Payments (external link)
- Ant - Chargeback Liabilities (external link)
- Monetization Gateway beta (external link)
- Release v2026-08-25 (external link)
- Mastercard Checkout Solutions: Release History (external link)