Ismn validate

ismn-validate · version 1.0.0 · Identifiers & check digits · free, no key needed

Validate an ISMN's EAN mod 10 check digit in M-form or 979-0 form and return the canonical 13-digit form.

Use when you need to: validate an ismn · check ismn check digit · convert m-form ismn to 979-0.

Decide before calling

Read the versioned contract and the supported scope below. Reuse ismn-validate@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use ismn-validate@1.0.0 for validate an ismn. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

• validate an ismn
• check ismn check digit
• convert m-form ismn to 979-0
• is this music publication number valid
• ismn checksum validator
• verify sheet music identifier
• is 979-0 a valid isbn prefix

Not supported

• looking up which publication an ISMN actually identifies
• validating an ISBN or ISSN (see isbn-validate / issn-validate)
• accepting a 979-0 form with the M-form prefix mixed in

Behavior

• Normalization: remove every '-' and ' ' from ismn first; the 17-byte limit and 1-byte minimum apply to the original, unstripped ismn.
• Character counting: every length, position and 'character' counts Unicode code points, not UTF-16 code units, so the echoed ismn13 and check_digit never split a surrogate pair.
• Two stripped lengths are accepted: 10 (M-form: character 1 must be literal 'M', characters 2-10 are 9 digits including the check digit) or 13 (all digits, current form). Any other stripped length is reason wrong_length, checked first.
• 13-digit-form only: once the charset passes, characters 1-4 must be '9790', else reason unknown_prefix.
• ismn13 and check_digit are always reconstructed from the raw positions whenever the stripped length is 10 or 13, regardless of charset, prefix or check-digit validity; both are null only when length already failed. For M-form, ismn13 is 9790 + characters 2-9 + a freshly computed check digit (computable once characters 2-9 are digits); for the 13-digit form, ismn13 is simply the stripped input.
• Check digit (evaluated only once the charset, and for the 13-digit form the prefix, both pass): weight the first 12 digits (of the 13-digit form, or of 9790+characters2-9 for M-form) alternately 1,3,... (the isbn13/EAN-13 rule); a mismatch with the actual 13th digit (or M-form character 10) is reason check_digit_mismatch.
• valid is true only when length, charset, (for the 13-digit form) the prefix, and the check digit all pass, in that order; only one reason is ever returned.

Input

• ismn (string, required): min length 1; max length 17

Output

• valid (boolean, required)
• reason (one of null, "wrong_length", "invalid_character", "unknown_prefix", "check_digit_mismatch", required)
• ismn13 (string or null, required): min length 13; max length 13
• check_digit (string or null, required): min length 1; max length 1

Limits

• max ismn bytes: 17

Example

Request input:

{
  "ismn": "M-2306-7118-7"
}

Response:

{
  "result": {
    "valid": true,
    "reason": null,
    "ismn13": "9790230671187",
    "check_digit": "7"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "ismn-validate",
  "version": "1.0.0",
  "input": {
    "ismn": "M-2306-7118-7"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/ismn-validate/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"ismn":"M-2306-7118-7"}'

The machine-readable contract is at /v1/tools/ismn-validate/versions/1.0.0.

CLI

node cli.mjs run ismn-validate 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• Isin validate: Validate a 12-character ISIN's ISO 6166 Luhn check digit and parse its country prefix, NSIN and NSIN scheme.
• Issn validate: Validate an 8-digit ISSN's mod 11 check digit (X allowed) and compute its 977-prefixed EAN-13 barcode form.
• Checkdigit validate: Validate a full value's trailing check digit(s) against a named algorithm (Luhn, Verhoeff, Damm, ISO 7064, GS1, mod 10).
• Figi validate: Validate a 12-character FIGI's structure, forbidden-prefix rule and Modulus 10 Double Add Double check digit.
• Iccid validate: Validate a 19/20-digit ICCID's Luhn check digit, require the 89 major industry id, split issuer/account digits.
• Imo number validate: Validate a 7-digit IMO ship identification number's weighted mod-10 check digit, with or without the 'IMO ' prefix.