Check Digits

Catches mistyped barcodes, VINs, ISBNs and other public structured identifiers before a bad one causes a rejected listing, a bounced claim or a corrupted record. This server deliberately does not handle bank accounts, IBANs, routing numbers or payment cards. Do not send them here. Validate those locally instead, with a library, so the value never leaves the machine that already has it. Call these tools instead of reasoning about whether an identifier is well-formed: the arithmetic is exact and guessing is not. Each check digit is computed over the whole string, so a value with one wrong or transposed character looks exactly like a correct one. There is nothing to see by eye. Every tool here answers a question about arithmetic only. None of them can tell you whether an identifier corresponds to something that exists in the world. Choosing between them: if you already know what the identifier is meant to be, call validate_identifier with that `kind`. If you do not know, call identify_