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

The annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered without the description. The description adds that the tool returns official value and recent trend, but it discloses no additional behavioral caveats such as data sources, rate limits, or freshness 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 very short and front-loaded with the core purpose before the usage trigger. The second sentence is not waste, but it is somewhat broad; overall it is appropriately compact for a simple read-only tool.

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-only tool with no output schema, the description covers what the tool returns and gives a usage trigger. However, it leaves the car_id parameter underspecified and does not mention when not to use the tool, so an agent still has to infer part of the invocation contract.

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 0%, so the description must compensate, but it only says 'deste carro' and never explicitly explains what car_id means, how to obtain it, or that it must match a previously selected car. The parameter name car_id is self-explanatory up to a point, but the description adds almost no semantic value beyond that.

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 identifies a specific resource—official FIPE valuation for a given car—and adds that it includes recent trend, which distinguishes it from broader market-stat siblings. It lacks an explicit verb like 'get' or 'returns', but the noun phrase is still clear enough for an agent to know what the tool produces.

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' explicitly states when the tool should be used, which is a clear trigger for an agent. It does not name sibling alternatives or exclusions, so it doesn't meet the 5-level bar, but the context provided is meaningful and non-ambiguous.

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