Agentic Rails Atlasby merces.ai

Research atlas by merces.ai

Agentic Rails Atlas

An observatory for agent identity, checkout and payment rails. A research tool by merces.ai that explains eight agent identity, intent, checkout and payment protocols, each with sourced claims, diagrams, a plain-language version and simulations you can run in the browser.

Start hereSkip to the protocol list

Protocol universe

The universe is a wide chart. The protocol list below has the same content.

Persona: All personas
Dim protocols by relevance to a persona

Hover or focus a protocol to see its card and relations. Arrow keys move between protocols; Enter opens one.

ERC-8004Agent identity and reputation registriesStatus: Draftx402Machine paymentsStatus: LiveVisa TAPSigned agent requests for card checkoutStatus: MixedACPAgent checkout against the merchant's APIStatus: BetaUCPAgent checkout and ordersStatus: LiveMPPHTTP Payment authenticationStatus: MixedAP2Signed purchase mandatesStatus: DraftAgent PayAgentic tokens for registered agentsStatus: Pilot

Fill: layer family

  • Identity and trust
  • Authorization and intent
  • Checkout and orders
  • Payment execution and credentials

Ring: rails

  • Card network
  • Crypto-native
  • Rail-agnostic or multi-rail
  • Bank rails

Status

  • Draft
  • Beta
  • Pilot
  • Live
  • Mixed

Relation lines (on hover or focus)

  • Compatible with
  • Embeds
  • Complements
  • Competes with
  • Same steward

Size

Equal base size, a little larger for each extra layer covered. Not sized by adoption.

Protocols

The same 8 protocols as the universe, in reading order.

  1. ERC-8004: Trustless AgentsAgent identity and reputation registries

    A Draft Ethereum standard that gives AI agents a portable on-chain identity (an ERC-721 token that points to a registration file) and a public feedback log. A third registry for independent validation is specified but not officially deployed. It moves no money, which is why it is often paired with x402.

    Family
    Identity and trust
    Layer
    Identity and trust
    First announced
    Latest version
    Draft text last changed 2026-01-25 (Updates from community feedback); registry contracts report version 2.0.0,
    DraftCrypto-nativeRail-agnostic
  2. x402Machine payments

    An open protocol that turns HTTP 402 Payment Required into a working pay-per-request flow. The server quotes a price, the client signs a payment, and a facilitator verifies and settles it, most often in USDC. Originated at Coinbase and governed since 2026 by the x402 Foundation, a Linux Foundation project.

    Family
    Payment execution and credentials
    Layer
    Settlement rails
    First announced
    Latest version
    Spec v2.0 (x402Version 2); SDK @x402/core 2.28.0 on 2026-09-29,
    LiveCrypto-nativeMulti-rail
  3. Visa Trusted Agent ProtocolSigned agent requests for card checkout

    A Visa specification that lets a merchant's site tell an approved AI agent from an unknown bot. The agent signs each web request with RFC 9421 HTTP Message Signatures, tagged for browsing or for paying, and can attach signed consumer and payment objects at checkout. Built with Cloudflare as part of Visa Intelligent Commerce, it identifies agents and moves no money by itself.

    Family
    Identity and trust
    Layer
    Identity and trust
    First announced
    Latest version
    Unversioned specification (launched 2025-10-14); sample code last changed 2025-10-28,
    MixedCard network
  4. Agentic Commerce Protocol (ACP)Agent checkout against the merchant's API

    The Agentic Commerce Protocol, from OpenAI and Stripe, defines how an AI surface runs checkout against a merchant's own REST API and passes a scoped, single-use payment token. It launched with ChatGPT Instant Checkout on 2025-09-29. Since March 2026 ChatGPT uses it mainly for product feeds and discovery, with checkout on the merchant's side.

    Family
    Checkout and orders
    Layer
    Checkout and orders
    First announced
    Latest version
    2026-04-17 (dated spec folder; no Git tag or release; edited after release),
    BetaCard networkRail-agnostic
  5. UCPAgent checkout and orders

    The Universal Commerce Protocol lets any agent read a store's published profile, agree on the capabilities both sides support, and run checkout, cart and orders over REST, MCP, A2A or an embedded UI. The store stays merchant of record and payments arrive as opaque tokens. Google launched it with Shopify and others in 2026, and it powers checkout in AI Mode and Gemini.

    Family
    Checkout and orders
    Layer
    Checkout and orders
    First announced
    Latest version
    v2026-08-25 (dated release; SDKs @ucp-js/sdk 0.5.1 and ucp-sdk 0.5.0),
    LiveRail-agnosticCard network
  6. Stripe MPP (Machine Payments Protocol)HTTP Payment authentication

    The Machine Payments Protocol, co-authored by Tempo and Stripe, adds a Payment authentication scheme to HTTP 402. A server issues a challenge, the client pays through a named method and retries with a credential, and the server returns a receipt. Charges and subscriptions are specified intents; metered sessions are defined per method. Rails include Tempo stablecoins, Stripe Shared Payment Tokens, Visa network tokens and Lightning.

    Family
    Payment execution and credentials
    Layer
    Payment credential
    First announced
    Latest version
    Core draft-httpauth-payment-01 (2026-09-09); mppx 0.13.4 on 2026-10-08,
    MixedMulti-railCrypto-nativeCard network
  7. AP2Signed purchase mandates

    Signed mandates that prove what a user authorized an agent to buy. Version 0.2 has Checkout and Payment Mandates, each closed (exact values) or open (constraints). Created at Google, donated to the FIDO Alliance on 2026-04-28, and carried inside UCP as an extension; live use is unverified.

    Family
    Authorization and intent
    Layer
    Intent and authorization
    First announced
    Latest version
    v0.2.0 (specification titled Agentic Payment Protocol v0.2),
    DraftRail-agnostic
  8. Mastercard Agent PayAgentic tokens for registered agents

    Mastercard's proprietary program for agent payments. Registered agents get agentic tokens built on Mastercard tokenization and limited by the consumer, and merchants recognize those agents from signed web requests. Verifiable Intent, a separate open specification, adds signed proof of what the user approved. Named transactions so far are pilots or first transactions.

    Family
    Payment execution and credentials
    Layer
    Payment credential
    First announced
    Latest version
    No program version numbers. Verifiable Intent 0.1 (tag v0.1.0 on 2026-03-05; breaking renames on main on 2026-04-20 under the same label),
    PilotCard networkMulti-rail

Changed in the last 60 days

Timeline events dated to , newest first.

  1. ERC-8004: Trustless AgentsSingle externally owned account owns the proxies on Ethereum and Base
  2. MarketObserved: x402.org counter unchanged, 8004scan passes 561,000 registrations
  3. StandardsERC-8226 adds per-asset mandates
  4. Stripe MPP (Machine Payments Protocol)mppx 0.13.4 released
  5. PolicyMAS issues Guidelines on AI Risk Management
  6. AP2TypeScript SDK pull request closed unmerged
  7. x402Cloudflare Monetization Gateway closed beta
  8. Mastercard Agent PayTrust Framework named; probability score testing in the US; Skyfire as KYA partner
  9. Stripe MPP (Machine Payments Protocol)Generic session intent pull request closed unmerged
  10. ERC-8004: Trustless AgentsCSOAI census of 505,635 agent ids
  11. UCPDraft lodging booking capability merged on main
  12. x402exact on Lightning (lnbtc)

Source details

    Loading the index.

    Enter open Esc close ? shortcuts