Agentic payment protocols - Darwin

Darwin Pay normalizes supported commerce protocols into the same bound payment interaction. The protocol describes how the merchant, agent, and provider coordinate; it never replaces user authority.

Protocol	What Darwin adapts
UCP	Capability discovery and interoperable commerce primitives between platforms, businesses, and payment or credential providers.
ACP	A seller-owned checkout session in which the seller calculates totals, manages inventory, processes payment, and remains merchant of record.
MPP	An HTTP `402 Payment Required` exchange that lets a client satisfy a payment challenge and retry with a scoped credential.

Preserve the protocol boundary

Darwin selects only a protocol advertised by the exact capability revision and payment interaction. It retains the merchant’s complete checkout state, handler identifiers, and confirmation result without translating free-form AI text into a payment proof.

Keep approval separate

A protocol can carry payment credentials or cryptographic authorization, but Darwin still enforces its own interaction binding, expected Action revision, expiry, and user decision. Changed terms require a new review. For an x402-specific exchange, see x402.

Last modified on September 22, 2026