httppayai

x402-catalog-history.ai-business-surface.workers.dev

Barcode check digit validator in one GET: EAN-13, UPC-A, EAN-8, ISBN-10 and ISBN-13 — returns the symbology, the check digit it carries, the expected check digit and whether the number is valid. curl: GET /barcode?code=9780306406157 (spaces and hyphens are ignored). Response: {"normalized":"9780306406157","symbology":"isbn-13","length":13,"check_digit":"7","expected_check_digit":"7","valid":true,"gs1_prefix":"978","isbn":{"format":"isbn-13","prefix":"978"}}. ISBN-10 accepts a trailing X. The verdict is check-digit arithmetic on the number you pass, not a registry lookup: a valid code does not prove that the product or book exists. Computed inside the Worker from the input; no upstream call, no account, no key. 0.001 USDC, one GET, one delivery. 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.