Tax ID Validation Skill

Overview

Tax ID Validator works by analyzing the format and structure of US Tax IDs, validating checksums and rules for SSN, EIN, and ITIN. It detects the type automatically, validates against known invalid patterns, and returns formatted and masked versions.

Live Test Tax ID Validation Skill Skill →

The tool

Once your client is connected to the VerveKit server, this appears in its tool list as TaxIDValidationSkill. 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.

Tool call

{
  "name": "TaxIDValidationSkill",
  "arguments": {
    "taxid": "123-45-6789"
  }
}

You do not name the tool yourself; the model picks it. Asking about 123-45-6789 in the terms this skill covers is enough for it to reach for TaxIDValidationSkill 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"
    }
  }
}

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.

Argument	Type	Description
`taxid`Required	string	The US Tax ID to validate (SSN, EIN, or ITIN format)

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.

Result

{
  "status": "ok",
  "error": null,
  "data": {
    "valid": true,
    "taxid": "123-45-6789",
    "type": "SSN",
    "type_full": "Social Security Number",
    "format": "XXX-XX-XXXX",
    "normalized": "123-45-6789",
    "digits_only": "123456789",
    "masked": "***-**-6789",
    "last4": "6789",
    "is_placeholder": true,
    "validation_details": {
      "format_valid": true,
      "area_number_valid": true,
      "group_number_valid": true,
      "serial_number_valid": true
    },
    "risk_score": 35,
    "risk_level": "medium",
    "error": null
  }
}

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.

Field	Type	Example	Description
`valid`	boolean	`true`	Whether the Tax ID passed validation checks
`taxid`	string	`123-45-6789`	The formatted Tax ID with standard formatting applied
`type`Premium	string	`SSN`	Abbreviated Tax ID type: SSN, EIN, or ITIN
`type_full`Premium	string	`Social Security Number`	Full name of Tax ID type like Social Security Number
`format`Premium	string	`XXX-XX-XXXX`	Expected format pattern for the Tax ID type
`normalized`	string	`123-45-6789`	Tax ID normalized to standard format with hyphens
`digits_only`	string	`123456789`	Tax ID with all non-numeric characters removed
`masked`	string	`*--6789`	Tax ID with sensitive digits masked for privacy protection
`last4`	string	`6789`	Last four digits of the Tax ID only
`is_placeholder`Premium	boolean	`true`	Whether the number is obvious filler (all-identical digits or a simple sequence like 123-45-6789) — true even when it structurally validates
`validation_details`	object	`{…}`
`validation_details.format_valid`Premium	boolean	`true`	Whether the Tax ID matches the expected format
`validation_details.area_number_valid`Premium	boolean	`true`	Whether SSN area number is valid (first three digits)
`validation_details.group_number_valid`Premium	boolean	`true`	Whether SSN group number is valid (middle two digits)
`validation_details.serial_number_valid`Premium	boolean	`true`	Whether SSN serial number is valid (last four digits)
`risk_score`Premium	number	`35`	Composite 0-100 risk score combining structural validity and placeholder detection (higher is riskier)
`risk_level`Premium	string	`medium`	Risk band derived from the score: low, medium or high
`error`	object	`null`	Error message if validation failed, otherwise null

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.

Status	What it means
`400` / `422`	The arguments did not validate. The message names the offending one.
`401`	The OAuth session is invalid or expired — reconnect the server.
`403`	Blocked by a key restriction or an IP allow-list. Never a bad identity.
`404`	This skill is not part of VerveKit. Check the catalog.
`429`	Out of credits, or a brief rate limit. The message tells them apart.

A call costs 10 credits each time the tool actually runs; a model that reasons about the tool without calling it costs nothing.

Use cases

Form Validation: Validate Tax IDs in online forms and applications to ensure correct format before submission
Compliance: Verify Tax ID format compliance for tax reporting, payroll processing, and financial services
Data Quality: Validate Tax IDs in databases during data cleaning and migration to identify invalid entries
Identity Verification: Check Tax ID format as part of identity verification processes while maintaining privacy with masking

Other ways to use Tax ID Validation Skill

Set up Tax ID 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.

Call it as a REST APIOne HTTPS endpoint and an x-api-key header, with SDKs for Node, Python and .NET.APIVerve →Reference →

Google Sheets or ExcelA =VERVE() formula fills a column — no script, no export, recalculates in place.VerveSheets →Reference →