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Protocol support

This page lists each protocol's status, pinned revision and implemented subset. Each protocol's page describes that subset in detail.

Support matrix

Protocol Status Revision Implemented subset
HTTP Supported native resource routes and rail-specific payment headers
MCP Supported MCP 2026-07-28 and 2025-11-25 through @modelcontextprotocol/server@2.3.0 tool discovery, invocation, payment-required and error mapping
x402 Supported x402 v2, @x402/core@2.25.0, @x402/evm@2.25.0, @x402/svm@2.25.0, @x402/near@2.25.0 exact on EVM through EIP-3009 or Permit2, on Solana, and on NEAR (partial): challenge, verification, settlement and replay binding
A2A Experimental v1.0.1; negotiation 1.0; JSONRPC binding Agent Card, SendMessage, paid flow and the x402 extension
ACP Experimental stable snapshot 2026-04-17; REST binding discovery and the five checkout operations
AP2 Experimental v0.2.0, tag 2026-04-28, commit b4587ac; Direct mode closed Checkout Mandate verification before settlement
MPP Experimental drafts at tempoxyz/mpp-specs@806fdb8; mppx@0.13.1 charge/evm/EIP-3009 over HTTP, MCP and A2A
UCP Planned - no implementation

Experimental components are disabled unless configured and support only the subsets their pages describe. Planned means there is no adapter or endpoint.

AP2 is an authorization method, not a transport or payment rail. It appears in authorizationProviders in gateway discovery and has no AP2-specific mount or discovery endpoint. See AP2.

An AP2-gated resource still requires its configured payment proof. A mandate authorizes the purchase but does not settle it.

GET /.well-known/agent-commerce reports descriptors for registered adapters and providers, including supportedSpec, capabilities, unsupported and status. When enabled, A2A, ACP and AP2 also print their detailed unsupported lists in agent-commerce doctor.

Protocol pages

  • HTTP surface: routes, and the payment headers each rail uses on the invoke route
  • MCP: tools, payment over MCP, and exclusions
  • A2A: invocation and payment, the x402 extension, results, and exclusions
  • ACP: headers, checkout operations, the payment boundary, idempotency, errors, discovery, and exclusions
  • x402: the exact scheme on EVM, Solana and NEAR, several options, payment flows, and mainnet guardrails
  • MPP: the pinned drafts, the charge profile, payment flow, problem documents, and exclusions
  • AP2: mandate verification before a paid resource settles

Adding an integration

See contributing-adapters.md. Adapter and provider implementations keep protocol-specific logic outside src/core; new protocol or rail names require an approved frozen-contract change.