...It’s maintained by OpenAI and Stripe and licensed under Apache-2.0, with the goal of being easy to adopt alongside a merchant’s existing commerce stack rather than replacing it. The repository organizes the spec as human-readable RFCs plus machine-readable OpenAPI and JSON Schema definitions, along with worked examples and a changelog so integrators can track breaking changes. Practically, ACP defines three main pieces; a Product Feed for discovery, an Agentic Checkout API for stateful, in-conversation checkout, and a Delegated Payment flow so a merchant’s existing PSP securely handles payment credentials and settlement. ...