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

Annotations already mark the operation as readOnly, idempotent, and non-destructive. The description adds significant behavioral context: it reveals the pay-per-query cost model, the absence of credentials, the public nature of the data, and the LGPD compliance responsibility. This goes well beyond the annotations and helps the agent anticipate side effects (cost) and legal constraints.

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 description is a compact three-sentence paragraph. The main purpose is front-loaded in the first sentence, followed by practical and legal context. It is not overly verbose, though the LGPD sentence could be seen as extra for an AI agent, but it remains relevant for data privacy compliance.

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 simple read-only query tool with three parameters and no output schema, the description covers the purpose, identifiers, cost, authentication, data source, and legal aspects. The only notable gap is the lack of explanation for the 'completo' parameter and return value structure, but neither is critical for basic invocation.

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 description explains that Placa and Chassi are vehicle identifiers used to fetch data, partially compensating for the 0% schema coverage. However, it does not clarify the optional 'completo' boolean parameter, and the phrasing 'placa ou chassi' is ambiguous given that both are required in the schema. This leaves some parameter semantics under-specified.

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 clearly states the tool's function: 'Dados de um veículo a partir da placa ou do chassi, com o valor de mercado na tabela FIPE' – a specific verb ('consultar' implied), resource (vehicle data via plate/chassis), and output (FIPE market value). It distinguishes itself from the unrelated sibling tools (authenticate, marketplace, etc.) by focusing on a unique vehicle lookup purpose.

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 provides practical usage context: it is hosted by the platform, requires no credentials, and costs prepaid credit per query. It also clarifies that the data is public access, which sets expectations for when this tool is appropriate. However, it does not explicitly mention alternatives or exclusions, though none of the sibling tools serve a similar purpose.

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