PESEL/NIP/REGON Validator

regon_validate

Validates the checksum of a 9- or 14-digit Polish business registry number (REGON). 9-digit: weights 8 9 2 3 4 5 6 7 over the first 8 digits, sum mod 11 (10 mapped to 0) must equal the 9th digit. 14-digit: the first 9 digits must themselves be a valid 9-digit REGON, and weights 2 4 8 5 0 9 7 3 6 1 2 4 8 over the first 13 digits (sum mod 11, 10 mapped to 0) must equal the 14th digit.

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": "regon_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

A3.9/5.0

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. It fully discloses the checksum algorithm for both 9- and 14-digit numbers, including weight sequences, modulo arithmetic, and how remainder 10 is handled. This is detailed, transparent, and gives the agent full understanding of the validation logic.

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

Conciseness4/5

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

The description is concise—two sentences—and front-loads the core purpose before detailing the algorithm. It could be slightly more efficient by omitting the algorithm details or moving them elsewhere, but for a validation tool, including the algorithm is justified and well-structured.

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

Completeness4/5

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

Given that there is no output schema referenced (though context says 'Has output schema: true', no details are provided), the description adequately explains input validation logic. However, it does not mention what the output looks like (e.g., returns a boolean or error message), which would be helpful for completeness.

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 description coverage is 100% and there is only one parameter, already described as 'digits-only identifier to validate (no spaces or dashes)' in the schema. The description adds no extra semantic meaning beyond what the schema provides, so the baseline of 3 is appropriate.

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?

The description clearly states that it validates the checksum of a Polish business registry number (REGON). It specifies the exact digit lengths (9 or 14), unlike siblings nip_validate or pesel_validate, making it well differentiated.

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

Usage Guidelines3/5

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

The description explains what the tool does but offers no guidance on when to use it versus nip_validate or pesel_validate. For example, it could mention that this is for business entities, while PESEL is for individuals and NIP is for tax identification, but it does not.

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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