How machines discover, buy, sell and pay
x402 is strategically important. It is not the whole map. Records exist only where public evidence supports them.
payment · live · reported
x402
An open protocol that uses HTTP 402 so a client can pay a server, usually in USDC, and retry. Named for the reserved HTTP status Payment Required.
12 sourced archive records
payment · announced · reported
Machine Payments Protocol (MPP)
An open standard co-authored by Stripe and Tempo. Agents request a resource, receive a 402-style payment request, authorize, and the merchant can see the payment like any other PaymentIntent.
5 sourced archive records
discovery · live · reported
Model Context Protocol (MCP)
Open-sourced by Anthropic on 25 November 2024. MCP is a discovery and execution protocol. It is not itself a payment protocol.
1 sourced archive record
wallet · announced · reported
Visa Intelligent Commerce
Visa’s agent-commerce wrapping: a tokenized card with user instructions. The shared design with x402 and MPP is policy-plus-envelope spending; the rails differ.
1 sourced archive record
commerce · announced · reported
Agentic Commerce Protocol (ACP)
Stripe has described an Agentic Commerce Protocol alongside MPP and x402 support. zFinia files it as a named commerce interface, not as a verified settlement census.
1 sourced archive record