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

With no annotations, the description carries the full behavioral burden and discloses important traits: only corporate/association data is ingested, not-found is not equivalent to invalid, and registered responses include name and address derived from corporate number data or null. It does not cover operational details such as authentication, rate limits, or pagination, but the domain-specific caveats are strong.

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 front-loaded with purpose, followed by data-scope caveats and response details, so most sentences earn their place. The final input example duplicates the schema's own example and is unnecessary, keeping it from a higher score.

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?

There is no output schema, so the description must explain return values; it does describe that registered responses include name and address, when those are null, and that not-found responses have both null. It also mentions date-bearing verification for registration/cancellation/expiration, though it does not fully specify the output shape for those date fields.

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?

Schema description coverage is 100%, and the schema already documents the single parameter with the T + 13-digit format and an example. The description adds the same input example and format, but no semantic meaning beyond what the schema provides, so the baseline of 3 applies.

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 states a specific verb and resource: verifying qualified invoice issuer numbers (T + 13 digits) for registration, cancellation, and expiration with dates. It clearly scopes the data to corporations and associations, but it does not explicitly differentiate itself from sibling corporate-lookup tools by name or contrast.

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?

It gives a clear when-not condition: sole proprietor numbers will not be found because only corporate/association data is ingested, and points to the public site as an external alternative. It also warns not to treat 'not found' as invalid. However, it offers no guidance on choosing among the sibling corporate lookup tools.

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