How do AI agents pay for APIs?

Agents receive HTTP 402 with machine-readable payment terms, send USDC on Base, and retry with a payment proof header such as X-PAYMENT-TX.

x402 is the agent payment pattern built on HTTP 402 Payment Required for pay-per-call APIs without traditional API keys.

GUIDE · AI AGENT PAYMENTS

How to charge AI agents for your API

Agents do not want API keys and monthly plans. They want a machine-readable price, a wallet, and a receipt. HTTP 402 + x402 is that contract.

When unpaid, respond 402 with network, asset, payTo, and amount (atomic USDC). Agents parse this automatically.

Agent pays USDC on Base, retries with X-PAYMENT-TX (sovereign) or facilitator X-PAYMENT. You verify and return data.

app.use('/premium', x402({ price: '0.001', payTo: '0x…', freeForHumans: true }))

Commodity snacks: $0.001. See the pricing oracle.

No. freeForHumans lets browsers through while bots/agents pay.

No. Settlement is on-chain USDC. See Stripe vs crypto for APIs.

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