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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description usefully adds the auth requirement (account or guest), which annotations do not convey, but says nothing about result volume, scoring, or pagination.

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?

One compact sentence with the action front-loaded and no filler. It is efficient, though the trailing auth clause is tacked on rather than structured as separate guidance.

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 single-parameter read tool with full schema coverage and rich annotations, the essentials are present. With no output schema, however, the description should say something about what a search returns (matching behaviour, result list shape), which is omitted.

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 single parameter already documents "Full CNPJ or a name of 3 to 120 characters." The description only restates the accepted input types, adding no format or matching-behaviour detail beyond the schema.

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?

States a specific verb ("Searches") and resource ("the company registry") plus the two search keys, so the agent knows exactly what the tool does. It does not, however, distinguish itself from near-neighbours such as consulta_cnpj or list_my_companies, which also surface company data.

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 only guidance is an access prerequisite ("requires an account or a guest"). There is no when-to-use/when-not framing and no mention of the obvious alternatives (list_my_companies for saved companies, consulta_cnpj for raw registry lookups), leaving routing to inference.

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