2s.io

● healthy general

Validate an ISIN (International Securities Identification Number, ISO 6166): 2-letter country prefix + 9-char NSIN + Luhn check digit. Returns {valid, isin, country, nsin, embeddedCusip (for US/CA), checkDigit, reason}. Catches transposed characters in security master data that a regex misses. Structure + checksum only. -- reliability 91.0/100 per Paygent Discover

How to call

cURL · x402-fetch / x402-axios will auto-handle 402

curl -X POST https://2s.io

/.well-known/x402.json

https://2s.io/.well-known/x402