x402 Agentic Payments

What x402 Is

x402 is an open standard for paying for things over HTTP. Coinbase created it in 2025, and it is now run by the x402 Foundation at the Linux Foundation. It uses the HTTP status 402 Payment Required, which has been part of HTTP for decades but was rarely used.

A payment works like this:

1. A client, such as an AI agent, sends a request.
2. The server replies with 402 and says how much to pay and how.
3. The client pays, usually with a stablecoin such as USDC, and sends the request again with proof of the payment. A stablecoin is a cryptocurrency whose value is tied to a regular currency, like the US dollar.
4. The server checks the payment and handles the request.

The client doesn't need an account or a signup first. This lets an AI agent pay for the services it uses on its own.

x402 on Tuna

Tuna plans to support x402, so that agents can pay for requests over HTTP. Until then, organizations pay with a credit card.