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x402 Payments

The standard protocol for machine-to-machine AI API payments.

What is x402?

x402 is a protocol extending the HTTP 402 Payment Required status code. It allows autonomous agents and decentralized systems to pay for their own API usage dynamically, without pre-funding centralized accounts with credit cards.

How it works

The x402 flow operates in four steps:

  1. Unauthenticated Request: The client makes an API request without an API key or auth token.
  2. 402 Payment Required: InferHood calculates the cost of the request (based on tokens, complexity, etc.) and returns a 402 Payment Required response containing a payment invoice/challenge.
  3. Payment: The client fulfills the payment on the designated chain (e.g., Robinhood Chain).
  4. Fulfillment: The client retries the request, including the payment receipt/proof in the Payment-Authorization header. InferHood verifies the payment and returns the result.

Payment Authorization Header

Once payment is complete, the client attaches the proof to the original request:

bash
curl https://api.inferhood.xyz/v1/chat/completions \
  -H "Payment-Authorization: x402-proof payload=..."

Robinhood Chain

Currently, InferHood supports settlement via the Robinhood Chain for minimal fees and sub-second finality. Ensure your agent wallet has sufficient R-USD balances.