Commerce — Accepting Agent Payments and Checkout

The agent-readiness dimension that accepts agent payments and checkout — x402, AP2, ACP and UCP — so an agent can transact with your site, not just browse.

What does the commerce dimension mean?

The commerce dimension lets an agent move value through your site: pay for a resource, complete a checkout or settle a transaction on a user's behalf. It comes last: an agent must already discover, read, be admitted to and act on a site before a payment makes sense. Access control charges for crawling; commerce handles purchase and settlement.

Which signals and standards does commerce cover?

Four protocols, one job each:

• x402 — revives HTTP 402, which RFC 9110 (IETF, 2022) still reserves for future use: the server answers an unpaid request with 402 plus a PAYMENT-REQUIRED header, the client retries with a PAYMENT-SIGNATURE header, and a facilitator's /verify and /settle endpoints settle it (x402 Foundation, 2026). Started at Coinbase, it now belongs to the x402 Foundation, launched under the Linux Foundation on 14 July 2026 with 40 member organizations (Linux Foundation, 2026).
• AP2 (Agent Payments Protocol) — announced by Google on 16 September 2025 with more than 60 organizations; it records a user's instructions as tamper-proof, cryptographically signed mandates backed by verifiable credentials, and can extend A2A and MCP (Google, 2025).
• ACP and UCP — the Agentic Commerce Protocol, released by Stripe and OpenAI on 29 September 2025 as an Apache-2.0 standard in which the business stays merchant of record (Stripe, 2025; agenticcommerce.dev, 2026) — behind ChatGPT Instant Checkout until OpenAI wound that in-chat checkout down on 24 March 2026 (Modern Retail, 2026); and the Universal Commerce Protocol, announced by Google and Shopify on 11 January 2026 with more than 20 endorsing retailers and platforms, likewise Apache-2.0 with AP2, A2A and MCP support built in (Shopify, 2026; ucp.dev, 2026).

How does the Agent-Readiness Audit score commerce?

It does not: none of the Audit's 18 checks tests a payment path, and its four scored categories are Discovery, Content, Capability and Trust (Agents Welcome, 2026). A commerce check would verify the handshake, not the shop: 402 with a machine-readable price and accepted method, then the resource once paid. This site runs that loop as a protocol-faithful demo with no real money: GET /api/premium/playbook answers 402 with x402Version 1 terms and a $0.10 price, POST /api/pay issues a token, and the retry with an X-Payment header returns the playbook. Commerce stays opt-in: it counts once you choose to sell to agents.

Commerce — frequently asked questions

What does HTTP 402 have to do with agent payments?

RFC 9110 reserves status 402 Payment Required for future use, and x402 and Cloudflare's pay-per-crawl use it as the signal that a resource costs money: the price travels in machine-readable form, so an agent can pay and retry without an account or a card form.

Does the Agent-Readiness Audit score commerce?

No. Its 18 checks cover Discovery, Content, Capability and Trust; a payment path is not scored. This site's x402 demo at /api/premium/playbook shows what such a check would test: a 402 with readable terms, then the resource after payment.

Which protocol should I implement first: x402, AP2, ACP or UCP?

It depends on what you sell. For per-request access to content or an API, x402 settles in plain HTTP. For a merchant checkout inside an AI assistant, UCP (Google and Shopify, with AP2 support built in) or ACP (Stripe and OpenAI, whose standalone ChatGPT checkout ended on 24 March 2026) defines the checkout.

Related: how x402, AP2, ACP and UCP divide the payment job · the x402 spec · Agentic Commerce & agent payments · x402 defined · the Agent Protocol Atlas · audit your site

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