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

The annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true and idempotentHint=false, so safety is covered. The description adds two things the annotations cannot express: the quota cost ('Consome 1 requisição') and the plan gate ('Plano Avançado'), both operationally important for an agent budgeting calls.

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?

Two short sentences, front-loaded with the resource and its returned fields, then the cost and plan constraint. Every clause carries information; nothing is filler.

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 one-parameter read tool with no output schema, the description covers outputs, quota cost and plan tier, which is nearly everything an agent needs. The remaining gap is that 'recentemente' is never defined - no date window or ordering is stated - so the agent cannot know how fresh the results are.

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 single parameter 'limite' is fully documented in the schema (range 1-100, default 20) at 100% coverage, so the schema carries the semantics. The description adds nothing about the limit or ordering, making the baseline 3 appropriate.

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 gives a specific verb and resource ('Lista empresas abertas recentemente') and enumerates exactly what each result carries (CNPJ, razão social, data de abertura, UF). It implies distance from the CNPJ-lookup siblings (ficha_cnpj, socios_cnpj) by being a discovery/list tool, but never names an alternative, so it stops short of explicit sibling differentiation.

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?

'para prospectar negócios novos' supplies a concrete use case, and 'Plano Avançado' flags an access prerequisite, which is more than most definitions offer. There is no statement of when not to use it or which sibling to pick when a specific CNPJ is already known.

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