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

Annotations cover the safety profile (readOnly, idempotent, non-destructive, closed-world read), and the description adds substantial behavioral context on top: partial-sum semantics, the role of `faltantes`/`origens`, the `rotulo` cases and the risk of misreading "ipva_apenas" as cost of ownership, and that `estimativa` is always true because depreciation is a statistical projection, not official FIPE data.

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?

Front-loaded with the core definition, then progressively narrower caveats. It is long and dense, but nearly every sentence carries a distinct constraint; minor redundancy around the partial-sum caveats.

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 no output schema and only safety annotations, the description fully carries the burden: it explains the returned fields (`total`, `faltantes`, `origens`, `rotulo`, `estimativa`), their interpretation, and the edge case of out-of-scope vehicle types.

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%, so `uf`, `ano` and `fipeId` are already documented in the schema. The description only indirectly reinforces parameter meaning (UF determining IPVA and energy tariff), so the baseline 3 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?

States a specific computed resource and its exact composition: "depreciação projetada + IPVA da UF + combustível (ou energia, em elétrico)". It also clearly delimits itself against siblings such as carpedia_preco_fipe and carpedia_plano_manutencao by saying what it does not include.

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?

Explicitly states the applicable vehicle scope (only cars and light commercial vehicles) and the behavior outside it ("para moto, caminhão ou ônibus responde sem dado e sem cobrança"). It also names exclusions (no insurance quote, no full maintenance cost), but does not route the agent to a named alternative tool.

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