MCP (Model Context Protocol)

Steward

Agentic AI Foundation (AAIF), a Linux Foundation directed fund formed 2025-12-09, with Anthropic contributing MCP

Status

Live

Primary source

Model Context Protocol Specification, version 2025-11-25 (external link)

What it is

MCP standardizes how an AI application talks to a server that offers capabilities. The client usually lives inside a chat product or coding agent, and the server exposes tools the client can call, resources it can read and prompts it can insert. Messages are JSON-RPC 2.0 between hosts, clients and servers, carried over stdio or Streamable HTTP. ^{Source [1]}

Status

MCP is live and uses dated specification revisions; the atlas reads revision 2025-11-25. ^{Source [1]} On 2025-12-09 the Linux Foundation announced the Agentic AI Foundation (AAIF), with Anthropic contributing MCP alongside Block’s goose and OpenAI’s AGENTS.md. The founding platinum members were Amazon Web Services, Anthropic, Block, Bloomberg, Cloudflare, Google, Microsoft and OpenAI. ^{Source [2]}

How it relates to the eight

For agentic payments MCP is the plumbing that other rails ride on. Several of the eight define how their messages travel inside MCP calls.

• x402 defines an MCP transport: a tool result with isError: true carries the PaymentRequired data, the client retries with payment in _meta["x402/payment"], and settlement comes back in _meta["x402/payment-response"]. ^{Source [3]} The project publishes an @x402/mcp package. ^{Source [4]}
• MPP has a draft JSON-RPC and MCP transport for its Payment authentication scheme, with capability advertisement and payment data placed in MCP’s _meta. ^{Source [5]}
• ACP added an MCP transport binding in its 2026-04-17 release; its OpenRPC file defines MCP tools that map one to one to the REST checkout operations, with authentication handled at the MCP server level. ^{Source [6, 7, 8]}
• UCP lists MCP as a transport with an OpenRPC schema, specifies Streamable HTTP rather than SSE, and applies the same RFC 9421 signature rules to MCP POST requests. ^{Source [9, 10]}
• ERC-8004 registration files accept an MCP service entry with endpoint and version, and feedback entries may name an MCP tool, prompt or resource. ^{Source [11]}
• AP2 samples run merchant, credentials provider and payment processor roles as MCP servers, and the AP2 FAQ says an SDK and an MCP server are being worked on. ^{Source [12, 13, 14]}
• For Visa TAP, Visa publishes MCP client and token manager packages for its Intelligent Commerce APIs; TAP itself does not depend on MCP. ^{Source [15, 16]}
• For Mastercard Agent Pay, Mastercard ships the @mastercard/developers-mcp server package, which is a general developer tool rather than an Agent Pay component. ^{Source [17]}

Status history

• 2025-11-25: specification revision 2025-11-25 released. ^{Source [1]}
• 2025-12-09: MCP joins the Agentic AI Foundation under the Linux Foundation. ^{Source [2]}

Relations at a glance

Back to the orbit

Sources

1. Model Context Protocol Specification, version 2025-11-25 (external link)Model Context Protocol. Specification, primary source. Published 2025-11-25. Accessed 2026-10-11.
2. Linux Foundation Announces the Formation of the Agentic AI Foundation (AAIF), Anchored by New Project Contributions Including Model Context Protocol (MCP), goose and AGENTS.md (external link)The Linux Foundation. Announcement, primary source. Published 2025-12-09. Accessed 2026-10-11.
3. x402 MCP transport (V2) (external link)x402 Foundation. Specification, primary source. Accessed 2026-10-10.
4. npm downloads API (last month) for x402 packages (external link)npm. Dataset, primary source. Accessed 2026-10-10.
5. Payment Authentication Scheme: JSON-RPC and MCP Transport (draft-payment-transport-mcp-00) (external link)Tempo Labs. Specification, primary source. Accessed 2026-10-11.
6. ACP changelog, version 2026-04-17 (external link)Agentic Commerce Protocol project. Specification, primary source. Published 2026-04-17. Accessed 2026-10-11.
7. MCP Transport Binding for Agentic Checkout (external link)Agentic Commerce Protocol project. Specification, primary source. Published 2026-02-19. Accessed 2026-10-11.
8. ACP OpenRPC schema for the MCP binding, 2026-04-17 (external link)Agentic Commerce Protocol project. Specification, primary source. Accessed 2026-10-11.
9. UCP Shopping Service MCP OpenRPC (v2026-08-25) (external link)UCP Authors. Specification, primary source. Published 2026-08-25. Accessed 2026-10-11.
10. UCP Message Signatures (v2026-08-25) (external link)UCP Authors. Specification, primary source. Published 2026-08-25. Accessed 2026-10-11.
11. ERC-8004: Trustless Agents (specification source, ERCS/erc-8004.md) (external link)Ethereum ERCs repository. Specification, primary source. Published 2026-01-25. Accessed 2026-10-11.
12. AP2 repository (README, METADATA, LICENSE) at e1ea56d (external link)Google (google-agentic-commerce). Repository, primary source. Published 2026-04-29. Accessed 2026-10-11.
13. AP2 repository x402 samples (external link)Google Agentic Commerce. Repository, primary source. Accessed 2026-10-10.
14. AP2 FAQ (external link)Google (google-agentic-commerce). Documentation, primary source. Published 2026-04-28. Accessed 2026-10-11.
15. visa/ai (formerly visa/mcp) repository: VIC MCP and API clients, vic-agent demo, skills (external link)Visa. Repository, primary source. Accessed 2026-10-11.
16. Visa advances agentic commerce with MCP Server, Acceptance Agent Toolkit (external link)Visa. Announcement, primary source. Published 2025-09-04. Accessed 2026-10-11.
17. npm registry: @mastercard/developers-mcp (external link)npm. Dataset, primary source. Accessed 2026-10-11.