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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the tool is known to be safe and non-destructive. The description adds practical behavior: it resolves a name to a corporate number, and mentions that Japanese names resolve more reliably than romanised ones—useful context. However, it does not disclose potential API quota limits or response format beyond field names. With annotations covering the safety profile, this is adequate but not rich.

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 a single sentence that is dense but readable, front-loading the key identifier (13-digit corporate number) and source. It lists many returned fields but does so efficiently. It is slightly long but every clause adds content; no filler. The structure is clear, though a bit of a run-on.

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?

For a read-only, idempotent, list-like profile tool with fully documented parameters and no output schema, the description covers the purpose, source, input variants, and a representative field list. It does not specify pagination or response structure, but these are less critical given the tool's simplicity and the annotations. The description is sufficient for an agent to call it correctly.

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 coverage is 100%, so both parameters are described in the schema. The description adds meaning beyond the schema by explaining the corporate_number parameter can be either a number or a name, and gives guidance on using Japanese names over romanised ones. It also clarifies the _apiKey parameter's purpose (using own quota) in the schema. This exceeds the baseline of 3.

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 states the tool's purpose: it retrieves a registry profile for one Japanese company using its 13-digit corporate number, from a specific source (gBizINFO/METI). It lists the data fields returned, distinguishing it from siblings like gbiz_company_search (searching) and gbiz_company_procurement (procurement). The verb 'returns' is specific and the resource is unambiguous.

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 implies usage: use when you need a company profile from the Japanese registry, but does not explicitly state when to use it over similar siblings like gbiz_company_records or gbiz_company_search. No explicit 'when not to use' or alternative routing is given. The context is clear but lacks exclusions for siblings that might also provide company data.

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