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What is x402?

x402 is an open protocol for paying for HTTP requests inline with a signed stablecoin transfer. Rye exposes an x402-native endpoint at https://x402.rye.com that accepts purchases from any x402-compatible client — instead of authenticating with a Rye API key, the caller pays for each request with a signed USDC transfer. It is built for AI agents and other automated clients that hold a crypto wallet but do not have a Rye developer account. It is a thin wrapper around Rye’s standard Checkout Intent flow — the same offer retrieval, order placement, and refund logic — exposed over the x402 wire format. If you already have a Rye API key, you do not need this endpoint. Use the standard Universal Checkout API — x402 is also available there as a payment method on /v1/checkout-intents/:id/confirm.

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When to use it

Use x402 if all of the following are true:
  • Your client signs HTTP requests from a crypto wallet (Base, Solana, or Tempo)
  • You do not have, or do not want to manage, a Rye API key
  • You are integrating with AgentCash or another x402-native runtime

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Base URL

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Endpoints

The exact amount due is quoted in the PAYMENT-REQUIRED header on each 402 response. GET is free so polling does not accrue cost.

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Flow at a glance

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Supported networks

USDC is the only accepted token on every supported network.

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Wallet identity

There is no Authorization header and no X-Wallet-Address header on paid calls. The wallet is whatever resolves from authorization.from inside the signed PAYMENT-SIGNATURE payload. A signed request is the authentication — payment and identity are the same.

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Discovery

The endpoint publishes an OpenAPI 3.1.0 document with x-payment-info annotations on each paid operation, so AgentCash and other x402 clients can discover prices and schemas without prior knowledge of the API:

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Next steps

Quickstart with AgentCash

Walkthrough using the AgentCash SDK

Endpoint Reference

Request and response shapes for each call