httppayai

x402-isin-check

Is this ISIN well formed? One GET applies the ISO 6166 check digit and returns valid, the supplied and expected check digit, the checksum total, the country code and name, and the 9-character NSIN. Malformed input is 400 before payment; a wrong check digit is 200 with valid=false. The algorithm is bundled in this Worker; no registry is queried, nothing is stored and the query is not logged. 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.