Protocol

x402

Draft

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01 / What it is

A payment protocol over the HTTP 402 status: a server answers with a price, the client pays with a stablecoin transfer and retries, so agents can buy API calls without accounts.

Payments per request. AP2 is the mandate-based purchase protocol.

02 / Adoption

Tools that speak x402

0 graded B or better · 1 in the catalog

1 tool

Coding +1

Circle Agent Stack

Wallet and USDC payment tooling agents call (x402-style autonomous payments), with starter kits for LangChain, Claude Agent SDK, OpenAI Agents SDK, Vercel AI SDK and Google ADK.

03 / Discussion

Discussion

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