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

Beyond the annotations, it discloses the billing model (paid packs, no free allowance), a meaningful non-recharge rule for already-revealed companies, and the fact that GET /api/revelar/:cnpj only checks access without charging. It also bounds the result: unmasking does not verify ownership, current contact availability, or refresh the source. That is substantial behavioral context an agent cannot get from readOnlyHint=false / destructiveHint=false.

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 pricing constraint is front-loaded, which is good, but the tail repeats itself: 'does not verify contacts or deliver a risk dossier' and 'does not refresh the source or provide a risk dossier' restate the same limitation twice. Two sentences could be cut without losing information.

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, non-read-only, unpriced-by-default tool with no output schema, the description covers cost model, preconditions, and the boundary of what is returned. What is still faint is the concrete shape of the payload (which fields of names/contacts come back), which matters slightly more given there is no output schema.

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?

There is only one parameter and the schema documents it at 100% coverage, including the unpunctuated 14-digit / alphanumeric format. The description adds no syntax or formatting detail beyond the schema, so the baseline 3 for high coverage 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 opening sentence gives a concrete verb and resource: unmasking partner names and contacts for a CNPJ. It also carves out scope against unnamed siblings by saying it 'does not verify contacts or deliver a risk dossier,' implicitly separating it from dossier_cnpj. It stops short of naming the sibling tools (consulta_cnpj, get_cnpj, dossier_cnpj) that an agent would otherwise confuse it with.

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 sets clear preconditions and exclusions: a paid lookup pack or per-company quote is required, there is no free allowance, and the tool is not for verification or risk dossiers. It also steers the agent to 'reuse the company already selected instead of integrating another source,' which is real usage guidance. The gap is that no alternative tool is named for the verification/dossier cases it rules out.

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