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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuinely useful behavioral context the annotations cannot: the 32000 sentinel means '0 km' and fipe_year_label should be shown instead of the raw code. It does not describe auth, rate limits, or trend window, but the sentinel disclosure is substantive added value.

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?

Three short sentences, front-loaded with the purpose before the field quirks. Slightly diluted by referencing fields absent from the schema, but no sentence is wasted.

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-param read tool with no output schema, the description does partially compensate by explaining the FIPE year encoding and label. However car_id is entirely unexplained and no return shape is hinted at, so it is adequate but with clear gaps.

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 coverage is 0% for the single required parameter car_id, and the description never explains it. Instead it documents output-side fields (fipe_year, fipe_year_label) that do not appear in the input schema, so the one parameter an agent must supply is left undocumented.

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 verb+resource: the official FIPE table value for a given car plus its recent trend. An agent can tell it retrieves valuation data, though it does not explicitly differentiate itself from siblings like get_market_stats or get_price_distribution.

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?

'Use para perguntas sobre a FIPE' is a vague, self-referential trigger with no when-not guidance and no named alternative. Given that siblings such as get_market_stats, get_price_distribution and get_market_position cover overlapping price territory, the absence of routing guidance is a real gap.

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