PESEL/NIP/REGON Validator

nip_validate

Validates the checksum of a 10-digit Polish tax identification number (NIP). Checksum uses weights 6 5 7 2 3 4 5 6 7 over the first 9 digits; sum mod 11 must equal the 10th digit. A sum mod 11 of 10 is itself invalid.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "value": "<value>"
    },
    "name": "nip_validate"
  }
}

Input Schema

Name	Required	Description	Default
`value`	Yes	digits-only identifier to validate (no spaces or dashes)

Output Schema

Name	Required	Description	Default
`valid`	Yes
`reason`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedAug 18, 2026

TDQS

A4.5/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description must carry the full burden of behavioral disclosure. It fully reveals the checksum algorithm and input format constraints, but stops short of stating whether the tool throws exceptions or returns a boolean, which would be ideal for a validation tool.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three concise sentences, each earning its place: purpose, algorithm, and an edge-case. No superfluous words.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the simple tool (1 parameter, no nested objects, single purpose) and the presence of an output schema (which would document return type), the description is complete and leaves minimal ambiguity for the agent.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% with one well-described parameter. The description adds value by specifying 'digits-only' and 'no spaces or dashes' beyond the schema, but baseline is 3 per guidelines since schema already covers the parameter well.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

Uses specific verb 'validates' and resource '10-digit Polish tax identification number (NIP)', clearly distinguishing it from sibling tools like pesel_validate and regon_validate.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Description explicitly covers when to use (validating a NIP), and sibling tools provide context for alternatives (PESEL, REGON). The algorithm details help the agent reason about correctness.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All PESEL/NIP/REGON Validator tools Inspect

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