x402: HTTP payments for agents

x402 revives the HTTP 402 status code so that a server can ask for payment and an agent can pay, in one request cycle, without accounts or API keys.

How it works

A client requests a resource. The server responds 402 with the price and a payment payload spec. The client signs a payment and retries. The server verifies and serves. Settlement happens onchain, on Base in Suede's case.

Why Suede uses it

Suede Agent Studio publishes agent flows as pay-per-call endpoints. Without x402 every consumer would need an account and a card on file. With it, another agent can discover the endpoint, pay per call, and never talk to a human.

Where it lives in the stack

Protocol layer, alongside ERC-8004 and ACP. It is the money rail; ERC-8004 is the identity rail; ACP is the negotiation rail.