The Agentic Commerce Protocol Stack

MCP + A2A on top, a payment layer beneath, merchant and rails at the base

The Agentic Commerce Protocol Stack MCP + A2A on top, a payment layer beneath, merchant and rails at the base Agent capability layer Payment layer Merchant + settlement Shopper · human intent · Architecture component Shopper human intent MCP · Model Context Protocol · Agent capability layer · tools / resources MCP Model Context Protocol tools / resources Peer Agents · Agent2Agent · Agent capability layer · discover + message Peer Agents Agent2Agent discover + message Agent Runtime · LLM orchestrator · Agent capability layer · MCP + A2A client Agent Runtime LLM orchestrator MCP + A2A client AP2 · Agent Payments Protocol · Payment layer · Intent - Cart - Payment AP2 Agent Payments Protocol Intent - Cart - Payment ACP · Agentic Commerce Protocol · Payment layer · feed - checkout - token ACP Agentic Commerce Protocol feed - checkout - token x402 · HTTP 402 onchain · Payment layer · stablecoin x402 HTTP 402 onchain stablecoin Merchant · storefront + PSP · Merchant + settlement Merchant storefront + PSP Payment Rails · cards - bank - chain · Merchant + settlement Payment Rails cards - bank - chain prompt tools + context A2A mandate 402 pay delegated token stablecoin settle Legend External Backend Security

Capability

  • • MCP wires the agent to tools, data, and context
  • • A2A lets agents discover and message peer agents
  • • Neither protocol moves money on its own

Payment layer

  • • AP2 signs Intent, Cart, and Payment mandates
  • • ACP drives agentic checkout with delegated tokens
  • • x402 settles onchain over HTTP 402 in stablecoins

How they compose

  • • The agent invokes a rail only when money must move
  • • AP2 rides as an A2A / MCP extension
  • • x402 attaches to A2A for onchain settlement

Architecture diagram • Built with Archify • Create yours ↗ • Hover to trace • R route • Click to focus • +/− zoom • M radar • [/] views • P play story • T theme • E export