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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds genuinely new behavioral context: the dataset only holds active companies, the call consumes 1 request, and it is gated to specific plans — cost and coverage caveats an agent cannot infer from annotations.

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 value proposition and the field list come first, followed by the sibling redirect and the cost/plan note; no sentence is filler. The field enumeration is long but each item is informative for deciding whether to call it.

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 convey return values and it does so explicitly through the field list. Missing only failure/not-found semantics for inactive or unknown CNPJs, which is a modest gap for a single-parameter read 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?

With a single parameter and 100% schema description coverage, the schema already explains the 14-character numeric-or-alphanumeric CNPJ and optional punctuation. The description adds no format, normalization, or error-handling detail beyond that, so the baseline 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 names the exact resource (dados cadastrais de uma empresa) and enumerates the returned fields — razão social, situação cadastral, CNAE, porte, Simples/MEI, endereço, contatos, quadro societário — which lets an agent distinguish it from ficha_cpf and socios_cnpj without opening any schema.

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 explicitly routes the agent away for a subset of data ('Para o telefone e o e-mail de cada sócio, use socios_cnpj') and warns that the base only contains active companies, implicitly defining coverage limits. It stops short of saying what to do when a CNPJ is inactive or not found, so it is clear but not fully exhaustive.

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