Card Validation Skill

Overview

Card Validator works by validating the card number against the Luhn algorithm and the brand's prefix and length rules. It identifies the card scheme, extracts the BIN and last four digits, checks the number against a list of known published test cards, and returns a risk score summarizing how safe the number is to trust.

Live Test Card Validation Skill Skill →

The tool

Once your client is connected to the VerveKit server, this appears in its tool list as CardValidationSkill. It is read-only and open-world — it fetches and never mutates anything on your side — so most clients call it without asking you to confirm.

{
  "name": "CardValidationSkill",
  "arguments": {
    "number": "4900264223817524"
  }
}

You do not name the tool yourself; the model picks it. Asking about 4900264223817524 in the terms this skill covers is enough for it to reach for CardValidationSkill on its own — naming it explicitly also works, and is the way to force the call.

Connecting

One server URL covers every skill in the catalog, including this one. Authorization is OAuth: the client opens a browser once, and there is no key to paste into a config file.

{
  "mcpServers": {
    "vervekit": {
      "url": "https://api.vervekit.com/v1/mcp"
    }
  }
}

https://api.vervekit.com/v1/mcp

Per-client setup — Claude, Cursor, VS Code, ChatGPT — is on the MCP setup page.

Arguments

These are the properties on the tool's inputSchema, so a well-behaved client validates them before the call is made. Premium arguments are accepted on every plan but only take effect on plans that include them.

What the model gets back

The result carries a structuredContent object matching the tool's declared outputSchema, so a client reads fields without parsing prose. status is "ok" and error is null on success; a null field means the value was not available for that input, not that the call failed.

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{
  "status": "ok",
  "error": null,
  "data": {
    "card": {
      "niceType": "Visa",
      "type": "visa",
      "patterns": [
        4
      ],
      "gaps": [
        4,
        8,
        12
      ],
      "lengths": [
        16,
        18,
        19
      ],
      "code": {
        "name": "CVV",
        "size": 3
      },
      "matchStrength": 1
    },
    "brand": "Visa",
    "cardNumber": "4900264223817524",
    "bin": "490026",
    "last4": "7524",
    "isValid": true,
    "isPotentiallyValid": true,
    "isTestCard": false,
    "riskScore": 0,
    "riskLevel": "low"
  }
}

Response fields

Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.

Failure modes

Errors come back as tool errors carrying a sentence the model can act on, not a bare status code. Error handling covers the full list.

A call costs 2 credits each time the tool actually runs; a model that reasons about the tool without calling it costs nothing.

Use cases

Dynamic Checkout Formatting

When shoppers type card numbers during checkout, frontend forms inspect partial validity to display matching brand icons and security code hints immediately.

Test Card Interception

Flag published processor test numbers in production checkouts before sending them to gateways, preventing failed authorization attempts or merchant penalty fees.

Payment Method Tokenization

Subscription billing services verify Luhn checksums and separate the bank identification number and last four digits before storing masked records in customer vaults.

Account Signup Screening

To block automated trial abuse, fraud prevention systems score incoming payment details and reject generated numbers that fail mathematical card validity checks.

Other ways to use Card Validation Skill

Set up Card Validation Skill on VerveKit, or reach the same source a different way. Your VerveKit account and credits work on all of them — one key, one balance.

Related

More in Data Validation: