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

Annotations already declare readOnlyHint=true, idempotentHint=true and openWorldHint=false, so the safety profile is fully covered without the description. The description adds the currency (reais) and the composition of the price list, but because an output schema exists this is largely restating return content rather than disclosing non-obvious behavior such as whether prices are static or localized.

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?

Single sentence, front-loaded with the usage trigger followed by the return contents. It is dense but every clause maps to a distinct pricing element; the enumerations ('mensal (com dias grátis)', 'Gestação completa (pagamento único)') are slightly list-like but earn their place.

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 zero parameters, an output schema, and full annotation coverage, the description supplies everything needed to select and invoke the tool. The only gap is the unaddressed boundary with list_features for 'o que o Nove+ libera'.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; baseline is 4. The description correctly frames the tool as taking no input by presenting it as a pure question-driven lookup.

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 states a concrete verb ('Retorna') and enumerates the exact resource contents: preço em reais, limites do plano grátis, Nove+ mensal e Nove+ Gestação com pagamento único. It is clearly a pricing/plan lookup and distinct from get_pregnancy_week, calculate_due_date and search_nove. It does not, however, distinguish itself from list_features, since 'o que o Nove+ libera' overlaps with a feature-listing tool.

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 first clause 'Use quando perguntarem quanto custa o app Nove ou o que é grátis' gives an explicit trigger condition tied to a user question type. That is a clear when-to-use signal, but no when-not-to-use or named alternative is given for the overlapping 'what Nove+ unlocks' case.

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