Imo number validate

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

Validate a 7-digit IMO ship identification number's weighted mod-10 check digit, with or without the 'IMO ' prefix.

Use when you need to: validate an imo ship number · check digit for imo number · is this imo number valid.

Decide before calling

Read the versioned contract and the supported scope below. Reuse imo-number-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 imo-number-validate@1.0.0 for validate an imo ship number. 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 imo ship number
• check digit for imo number
• is this imo number valid
• verify a vessel identification number
• imo number checksum calculator
• strip the imo prefix and validate the digits

Not supported

• a live IMO GISIS ship-registry lookup
• validating an IMO company or registered owner number (a different scheme)
• lowercase "imo " or a prefix without the trailing space (not recognized, evaluated as the whole candidate)

Behavior

• Only the exact 4-character literal prefix "IMO " (capital I, M, O, one space) is stripped, giving the candidate; any other form (lowercase, missing space) is left as the whole candidate, evaluated below unchanged.
• candidate.length != 7 returns reason wrong_length; length 7 but not all-digit returns reason invalid_character; both leave number/check_digit null.
• number = candidate, check_digit = candidate[6], populated once length and charset pass.
• Weighted sum over positions 1-6: digit * weight, weight = [7, 6, 5, 4, 3, 2]. expected check digit = sum mod 10, compared to check_digit for reason check_digit_mismatch.

Input

• imo (string, required): min length 1; max length 11

Output

• valid (boolean, required)
• reason (one of null, "wrong_length", "invalid_character", "check_digit_mismatch", required)
• number (string or null, required): pattern ^[0-9]{7}$
• check_digit (string or null, required): pattern ^[0-9]$

Limits

• max imo bytes: 11

Example

Request input:

{
  "imo": "IMO 9074729"
}

Response:

{
  "result": {
    "valid": true,
    "reason": null,
    "number": "9074729",
    "check_digit": "9"
  }
}

How to call it

MCP

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

{
  "id": "imo-number-validate",
  "version": "1.0.0",
  "input": {
    "imo": "IMO 9074729"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/imo-number-validate/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"imo":"IMO 9074729"}'

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

CLI

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

Get the client at /clients/cli/.

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