Agentic Commerce 101 — the 11 open protocols behind how AI agents shop

AI agents can now discover products, build carts, prove that a user authorised a payment, and pay on the user's behalf. This site explains each open protocol that makes it possible, in plain English and in code. Built by Andrew Vassili.

Discovery — how a query becomes shopping

• Catalog feed — the hidden registry that routes AI queries to the right merchants (OpenAI, Google, Shopify).

Tooling — how agents find tools

• MCP — Model Context Protocol (Anthropic, Nov 2024) — the common language every AI uses to talk to apps. Used by Claude, ChatGPT, Gemini.
• A2A — Agent2Agent (Google, Apr 2025 → Linux Foundation Jun 2025) — how AIs hand entire shopping jobs to other AIs.

Commerce — how AI agents shop

• ACP — Agentic Commerce Protocol (OpenAI + Stripe, Sep 2025) — how ChatGPT shows you real products from real stores.
• UCP — Universal Commerce Protocol (Google + Shopify, Jan 2026) — one shopping pipeline across every retailer at once.

Trust — who is allowed to act

• AP2 — Agent Payments Protocol (Google + 60 partners, Sep 2025) — a cryptographically signed permission slip an AI carries to the store.
• ACP Delegation — OAuth 2.1 + Dynamic Client Registration (RFC 7591) — how a store lets an AI act on your account.
• Visa Trusted Agent (2025 Pilot) — an agent-aware card token built on Visa Token Service.
• Mastercard Agent Pay (2025 Pilot) — Mastercard's fraud engine retrained for AI buyers.

Payment — how money moves

• Stripe Shared Payment Token (SPT) — a disposable card. One merchant, one use, one cap.
• Universal Cart (Shopify + Google, May 2026) — a multi-merchant cart that lives in Google Wallet.
• x402 — HTTP 402 machine-payable APIs (Coinbase) — USDC on Base for sub-cent micropayments between agents and APIs.

Author: Andrew Vassili. Site: agenticcommerce101.com.