check_vat_whitelist

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

With no annotations, the description bears the full burden of behavioral disclosure. It clearly states the output data points (status, name, REGON/KRS, bank accounts), but it does not mention error behavior (e.g., NIP not found), response format, or whether the operation is purely read-only. This leaves important gaps for an agent, but it is not contradictory or misleading.

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

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

The description is two sentences, both packed with relevant information. It front-loads the core purpose and usage context, with no wasted words. This is an excellent example of conciseness.

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

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

The tool has only two parameters and no output schema, so the description must convey both purpose and return data. It lists the key return fields and gives a concrete use case. However, it does not describe the response structure, possible error cases, or the exact handling of the date parameter, which would make it fully complete. Still, it is adequate for a straightforward lookup tool.

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

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

The schema already provides 100% coverage of parameter descriptions, so the baseline is 3. The description adds context about the purpose of the NIP and the use case, but it does not deepen the semantics of the 'date' parameter beyond what the schema states (ISO date, as-of date, defaults to today). Thus no additional value is added to justify a higher score.

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

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

The description clearly identifies the specific action ('Look up a Polish contractor by NIP') and the resource (Ministry of Finance VAT whitelist). It also lists the exact data returned (VAT registration status, legal name, REGON/KRS, bank account numbers), which distinguishes it from sibling tools like check_vies or validate_polish_id.

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

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

The description explicitly states when to use this tool: 'Use this to verify a business partner before paying an invoice.' This provides a clear use case and context. It does not explicitly name alternatives or exclusions, but the specific mention of the Polish whitelist implies when this is appropriate versus other tools, so it earns a 4.

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