lookup_cnpj

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is clear. The description adds the expected data categories returned, but does not disclose behavior around invalid CNPJs, response structure, or external data source variability. This is adequate but not especially 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 compact and well-structured: the first sentence states purpose and output, and the Args section precisely documents the sole input. There is no filler or redundant restatement of the tool name.

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?

With no output schema, the description compensates by listing the key returned fields and fully documenting the one required parameter. Annotations cover side effects and idempotency. Missing details like error behavior or exact response envelope are minor for a simple read-only lookup.

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 property has 0% description coverage, so the description carries the full documentation burden. It does so well by specifying that the CNPJ may be formatted or unformatted and providing two concrete examples. This is nearly all an agent needs for a single string parameter.

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 opens with a specific verb and resource: 'Look up a Brazilian company (CNPJ)' and names the data returned (legal name, address, status, business activity). This clearly distinguishes it from siblings like lookup_cep, list_banks, and get_holidays without needing to open their schemas.

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 use case is implied strongly by 'Brazilian company (CNPJ)', but there is no explicit guidance about when to choose this tool over alternatives or when not to use it. Sibling tools exist, yet the description does not acknowledge them or provide selection criteria.

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