httppayai

x402-seller-playbook

The seller's playbook for a live x402 endpoint: the exact 402 challenge to serve (v2 header and v1 body in one response), what the facilitator /verify really checks and the balance rule that rejects a valid signature, how a settled payment becomes a delivery, delivery evidence in three independent records, how to get listed where agent buyers search, and a plain-USDC page for human buyers who will never read a 402. Delivered as the full text plus a signed, expiring PDF download link. One GET, one delivery, no live upstream call, and the free sample at /guide/sample carries the whole protocol before you pay. The same playbook also covers the receiving side: USDC on Base with no account, no KYC and no third party between you and the buyer. A purchase is two calls by design: this first call returns 402 with the price and the payment terms, and you then repeat the same request with the PAYMENT-SIGNATURE header to receive the 200 delivery.