x402 Protocol
Developer Resources & Documentation
What is x402?
It gives the old HTTP status “402 Payment Required“ real purpose. When a website, API, or AI agent returns 402, it's not an error; it's a price tag. Example:
"This endpoint costs $0.01 USDC. Pay to continue."An AI agent can cryptographically sign a transaction and automatically send funds to the specified address to complete the payment.