x402 — Pay-per-request for agents

HTTP 402 has been reserved for 'future use' since 1999. The x402 standard finally claims it: when an agent hits a paid endpoint, you return 402 with a Payment-Required header describing the price, asset, and recipient. The agent settles payment (USDC on Base, Stripe, or Lightning via L402) and retries.

Why now

• Agents make billions of small requests — subscriptions don't fit.
• Stablecoin rails settle in seconds for fractions of a cent.
• It works without accounts, API keys, or OAuth flows.

The challenge header

HTTP/1.1 402 Payment Required
Payment-Required: eyJ4NDAyVmVyc2lvbiI6Mi... (base64 JSON)

{
  "x402Version": 2,
  "accepts": [{
    "scheme": "exact",
    "network": "base",
    "asset": "USDC",
    "amount": "0.01",
    "payTo": "0xYourWallet",
    "facilitator": "coinbase"
  }],
  "resource": "/api/premium"
}

Discovery: /.well-known/x402.json

Publish a static manifest so agents can find your paid endpoints before hitting them. This also makes you discoverable in the Bazaar registry.