Tax ID Validation Skill
The tool
Tax ID Validator checks the format and validity of US Tax IDs with detailed validation results, formatting, masking, and type detection for SSN, EIN, and ITIN.
Once your client is connected to the VerveKit MCP server, this appears in its tool list as TaxIDValidationSkill. It is read-only and open-world: it fetches, it never mutates anything on your side, so most clients will call it without asking you to confirm.
{
"name": "TaxIDValidationSkill",
"arguments": {
"taxid": "123-45-6789"
}
}What that looks like in a conversation
You don't name the tool — the model picks it. Asking about 123-45-6789 in the terms this source covers is enough for it to reach for TaxIDValidationSkill on its own.
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/mcpPer-client setup — Claude Desktop, 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.
| Argument | Type | Example | Description |
|---|---|---|---|
taxidRequired | string | 123-45-6789 | 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 can read fields without parsing prose. status is "ok" on success and error is null; a null field means the value wasn't available for that input, not that the call failed.
{
"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
}
}Fields
| 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 |
typePremium | string | SSN | Abbreviated Tax ID type: SSN, EIN, or ITIN |
type_fullPremium | string | Social Security Number | Full name of Tax ID type like Social Security Number |
formatPremium | 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_placeholderPremium | 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_validPremium | boolean | true | Whether the Tax ID matches the expected format |
validation_details.area_number_validPremium | boolean | true | Whether SSN area number is valid (first three digits) |
validation_details.group_number_validPremium | boolean | true | Whether SSN group number is valid (middle two digits) |
validation_details.serial_number_validPremium | boolean | true | Whether SSN serial number is valid (last four digits) |
risk_scorePremium | number | 35 | Composite 0-100 risk score combining structural validity and placeholder detection (higher is riskier) |
risk_levelPremium | 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 with a sentence the model can act on, not a bare status code.
| Status | What it means |
|---|---|
400 / 422 | The arguments didn't validate. The message names the offending one. |
401 | The OAuth session is invalid or expired — reconnect the server. |
403 | Out of credits. Not a bad key — the month's allowance is spent. |
404 | This skill isn't part of VerveKit. Check the catalog. |
429 | Brief rate limit. Retrying after a moment succeeds. |
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.
Frequently asked questions
Do I have to tell the agent to use TaxIDValidationSkill?
No. The tool's name and description are in the model's context once the server is connected, so it selects the tool when the question calls for it. Naming it explicitly works too and is useful when you want to force the call.
Does connecting the server expose every tool at once?
Yes — one connection lists the whole VerveKit catalog. Clients with a tool budget can usually filter the list; the credit cost is per call, so an unused tool costs nothing.
What does a call cost?
1 credit each time the tool actually runs. A model that reasons about the tool without calling it costs nothing.
Is there a REST version of this?
Yes — the same source is available as a plain HTTPS endpoint on APIVerve, linked above. Same data, same credits, same account.