x402 Explained: HTTP‑Native Micropayments for AI Agents (With Real Code)

Описание и применение

x402 — это протокол‑уровневый способ микроплатежей в HTTP, позволяющий агентам AI запрашивать услуги, получать 402 с заголовком Pay, оплачивать через Base и повторять запрос с заголовком Paid для получения ресурса.

Задача

Developers building autonomous AI agents need a lightweight way to charge or pay for fine‑grained services without adding a custom billing layer.

Результат

A minimal Express middleware demonstrates how to enforce x402 payments, charging 0.01 USDC per request and validating proof via a Pay/Paid header exchange.

Рабочий процесс

• Client sends GET /service without payment
• Server detects missing payment and responds 402 with Pay header containing payment URI
• Client executes payment instruction (e.g., sends USDC on Base) and obtains receipt
• Client retries original request with Paid header containing proof URI
• Server validates proof; if valid returns 200 OK with resource
• If proof invalid, server repeats 402 with updated Pay header

Доказательства

The HTTP status code 402 Payment Required was reserved in the original spec but never got a widely adopted implementation.

Источник

Below is a self‑contained example that charges 0.01 USDC per call.

Источник