x402 Payments

x402 is an open payment protocol that uses the HTTP 402 status code to enable programmatic, machine-to-machine payments over HTTP. It lets servers charge for API access without requiring traditional payment infrastructure, buyer accounts, or API keys.

When to use

• You want to charge for API access using onchain payments.
• You want to build AI agents that pay per request for API resources.
• You want to enable micro payments for premium data or services.
• You want to set up recurring payments with periodic budgets.
• You want to use MetaMask smart account delegations for x402 settlement.

Installation

npm install @x402/core @x402/fetch @metamask/x402 @metamask/smart-accounts-kit

For seller endpoints: