Payment card validate

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

Validate a payment card's Luhn check digit and detect its brand from its IIN, without returning the full number.

Use when you need to: validate a credit card number · check if this card number passes the luhn check · what card brand is this number.

Decide before calling

Read the versioned contract and the supported scope below. Reuse payment-card-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 payment-card-validate@1.0.0 for validate a credit card 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 a credit card number
• check if this card number passes the luhn check
• what card brand is this number
• is this a valid mastercard 2-series number
• detect visa mastercard amex discover from card number
• בדיקת מספר כרטיס אשראי

Not supported

• CVV, expiry date or cardholder-name validation
• looking up the issuing bank or country from the IIN
• card numbers with fewer than 12 or more than 19 digits after stripping spaces and hyphens
• brands other than Visa, Mastercard, American Express and Discover

Behavior

• stripped = number with every ASCII space (U+0020) and hyphen (-) character removed; every other character stays.
• If stripped is not all decimal digits 0-9, or its length is outside 12-19, return {valid:false, reason:'invalid_format', brand:'unknown', brand_candidates:[], length: stripped.length, luhn_valid:false, iin6:null, last4:null, data_version}.
• Otherwise iin6 is the first 6 characters of stripped and last4 the last 4; the full stripped number is never returned. luhn_valid is the ISO/IEC 7812-1:2017 Luhn check over stripped.
• brand_candidates, tested in the fixed order visa, mastercard, amex, discover: visa when stripped starts with '4'; mastercard when the 6-digit iin6 is in [510000,559999] or [222100,272099]; amex when the first 2 characters are '34' or '37'; discover when the first 4 characters are '6011', iin6 is in [622126,622925], the first 3 characters are '644'-'649', or the first 2 characters are '65'.
• brand is the single brand_candidates entry, else 'unknown'. valid = luhn_valid AND (brand is 'unknown' OR length is an allowed length for that brand: visa [13,16,19], mastercard [16], amex [15], discover [16,17,18,19]).
• reason is null when valid; 'luhn_invalid' when luhn_valid is false; 'wrong_length_for_brand' when luhn_valid is true but the length does not match the detected brand. data_version is always the pinned card-brand-iin-ranges dataset version.

Input

• number (string, required): min length 1; max length 40

Output

• valid (boolean, required)
• reason (one of null, "invalid_format", "luhn_invalid", "wrong_length_for_brand", required)
• brand (one of "visa", "mastercard", "amex", "discover", "unknown", required)
• brand_candidates (array of one of "visa", "mastercard", "amex", "discover", required): max items 4
• length (integer, required): min 0; max 40
• luhn_valid (boolean, required)
• iin6 (string or null, required): pattern ^[0-9]{6}$
• last4 (string or null, required): pattern ^[0-9]{4}$
• data_version (string, required)

Limits

• max number bytes: 40

Example

Request input:

{
  "number": "4111111111111111"
}

Response:

{
  "result": {
    "valid": true,
    "reason": null,
    "brand": "visa",
    "brand_candidates": [
      "visa"
    ],
    "length": 16,
    "luhn_valid": true,
    "iin6": "411111",
    "last4": "1111",
    "data_version": "card-iin-2026-09-28"
  }
}

How to call it

MCP

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

{
  "id": "payment-card-validate",
  "version": "1.0.0",
  "input": {
    "number": "4111111111111111"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/payment-card-validate/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"number":"4111111111111111"}'

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

CLI

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

Get the client at /clients/cli/.

Related tools

• Bic validate: Validate a Business Identifier Code's ISO 9362:2022 structure and parse its party prefix, country, location and branch.
• Checkdigit validate: Validate a full value's trailing check digit(s) against a named algorithm (Luhn, Verhoeff, Damm, ISO 7064, GS1, mod 10).
• Eu vat id validate: Detect the country from an EU/XI VAT id prefix and validate its format and, where defined, national checksum.
• Iban validate: Validate an IBAN's country, registry length, BBAN structure and MOD 97-10 check digits, and parse its bank/branch code.
• Iccid validate: Validate a 19/20-digit ICCID's Luhn check digit, require the 89 major industry id, split issuer/account digits.
• Gs1 key validate: Validate a GTIN-8/12/13/14, GLN, SSCC or GSIN's GS1 mod-10 check digit and look up its 3-digit GS1 prefix meaning.