ACP docs define merchant checkout-session REST endpoints

Five HTTPS JSON endpoints, not an HTTP 402 challenge.

Official Agentic Commerce Protocol seller documentation specifies REST checkout session create/get/update/complete/cancel endpoints. Later versions require capability declarations in checkout responses. This is a different machine contract from x402’s 402 + header retry.

Why it matters

A seller who “supports agents” may mean ACP checkout, x402 402, MPP, AP2, or Visa tokens. Discovery copy must name the rail.

Source: Agentic Commerce Protocol docs

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