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

Annotations already declare readOnly, idempotent, non-destructive semantics, so the safety profile is covered. The description adds operational behavior beyond the schema: default 5 with a hard cap of 8 results and the fact that cheaper_only filters to units priced below this one, which shapes expectations about output volume.

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-loads the core definition, then the use case, then the exclusion, then constraints. Dense but every clause carries routing or parameter information; the parenthetical constraint block is slightly compressed but not wasteful.

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 low-complexity read-only lookup with no output schema, the description covers purpose, routing, exclusions, and all meaningful parameter constraints. It does not describe the shape of returned listings, but the annotations plus the nature of the tool make that a minor gap.

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 carry parameter meaning, and it does for two of three: max_results (default 5, max 8) and cheaper_only (only cheaper than this one). car_id is only implied via 'DESTE carro', so it is not fully spelled out, but the schema marks it required and typed.

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+scope: 'Outras unidades à venda do MESMO modelo (mesmo carro, outros anúncios)'. It immediately distinguishes itself from sibling tools by ruling out 'modelos diferentes', which is exactly the boundary against get_alternative_models.

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?

Gives an explicit triggering user question ('tem opções mais baratas DESTE carro?') and an explicit exclusion ('NÃO use para sugerir modelos diferentes'), which routes the agent to the correct sibling. Both when-to-use and when-not-to-use are present.

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