Agentic Commerce Explained: ACP, AP2 and How to Make a Small Shop Buyable by AI Agents

🛒 Agentic commerce · Updated October 2026 · 4 min read · by Jacob Campbell

Until recently an AI assistant could recommend a product but a person still had to click through and check out. That is changing. In September 2025 two open protocols arrived for letting AI agents complete purchases: the Agentic Commerce Protocol (ACP), from OpenAI and Stripe, and the Agent Payments Protocol (AP2), from Google. This guide explains what each does, how they differ, and, more usefully for most shops, the groundwork that makes a store buyable by agents whichever protocol wins.

Key facts

• Sep 2025 — ACP and AP2 both announced
• ACP — OpenAI and Stripe: checkout inside the assistant
• AP2 — Google: verifiable payment mandates for agents
• Feeds first — Machine-readable products come before any protocol

The Agentic Commerce Protocol (ACP)

ACP was announced by OpenAI and Stripe in September 2025, alongside Instant Checkout in ChatGPT, and published as an open standard. It defines how an agent and a merchant exchange the steps of a purchase: creating and updating a checkout, confirming the order, and passing a secure payment token, while the merchant remains the merchant of record and keeps its own payment processing and customer relationship. Merchants share a product feed so the assistant knows what can be bought.

The Agent Payments Protocol (AP2)

AP2 was announced by Google in September 2025 with a long list of payments and technology partners. It focuses on trust and accountability: purchases are backed by mandates, cryptographically signed records of what the user authorised. An intent mandate captures the instruction (“buy these shoes under $120”); a cart mandate captures approval of the exact cart. AP2 is designed to work as an extension of A2A and MCP. See MCP vs A2A.

How they differ

• ACP is centred on a checkout flow between an assistant and a merchant, with payment handled through the merchant’s processor.
• AP2 is centred on proving user authorisation across agents, merchants and payment providers, and is payment-method agnostic.
• They are not mutually exclusive, and both are young. Expect versions to change.

The groundwork every shop needs anyway

1. Machine-readable products. Product and Offer JSON-LD on every product page with price, currency, availability, GTIN or SKU, shipping and return policy. See schema markup.
2. A clean product feed (the same data you would give Google Merchant Center).
3. Accurate stock and prices. Agents check; mismatches lose the sale.
4. Agent access. AI shopping and user-triggered agents must not be blocked. See robots.txt for AI crawlers.
5. Read-only MCP tools for search, availability and shipping questions. See adding an MCP server.
6. A checkout that a person can finish if the agent hands over.

Where small shops stand

Merchant programmes for agent checkout have typically started with large platforms and selected merchants, with smaller stores reached through their e-commerce platform or payment provider. For a small shop, the practical move today is the groundwork above, plus watching whether your platform or Stripe account offers agentic checkout. Shops on AIWebBuilding take payments through the owner’s own Stripe account (Stripe Connect), which keeps that path open.

Measuring readiness

WebAgentScan adds a Commerce pillar (up to 10 points) only when a site actually sells something, looking at machine-readable products and agent commerce readiness; see what WebAgentScan checks. Our own site declares an AP2 merchant extension on its A2A agent card, listed on our agent-ready page.

Related reading

• MCP vs A2A — Tools for one agent versus conversations between agents.
• Add an MCP server to your website — Tools, transports, annotations and security for a public site.
• Schema markup guide — JSON-LD for rich results, with working examples.
• robots.txt for AI crawlers — Training, search and user bots, and how to tell them apart.
• What WebAgentScan checks — The six scoring pillars, what each one tests, and how to read the result.
• AIWebBuilding — A website builder with the AI Indexing Pack core built into every published site.
• How this site is agent-ready — Our own live setup: the MCP endpoint, llms-full.txt, Markdown twins and the .well-known tree.

Frequently asked questions

What is the Agentic Commerce Protocol?

An open standard announced by OpenAI and Stripe in September 2025 that lets AI agents complete purchases with merchants, who remain the merchant of record and keep their own payment processing.

What is AP2?

The Agent Payments Protocol, announced by Google in September 2025, which uses signed mandates to prove what a user authorised an agent to buy. It is designed to work with A2A and MCP.

Is ACP the same as AP2?

No. ACP centres on the checkout flow between an assistant and a merchant; AP2 centres on verifiable user authorisation across agents and payment providers.

What should a small online shop do now?

Publish complete Product and Offer structured data, keep a clean product feed with accurate prices and stock, allow AI shopping agents, and consider read-only MCP tools.

Can AI agents buy from any website?

Not yet reliably. Agent checkout programmes started with larger platforms and selected merchants, and the protocols are still evolving.