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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds valuable behavioral context: deduplication across sources, approximate count of listings, automatic resolution of common brand/model names, and the fact that each result includes version, engine, consumption, opportunity status, ML guide price, and declared risks with the seller's phrase. This goes beyond what annotations provide.

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 single dense paragraph that front-loads the core purpose and then lists filters and result contents. It's long but every clause adds information about a distinct filter or output field. It could be slightly more structured (e.g., separating filters from output fields), but it's efficient for a tool with 24 parameters.

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 read-only search tool with 24 optional parameters and no output schema, the description covers the main search dimensions, the deduplication behavior, and the result fields. It doesn't explain pagination (page parameter) or default limit, but the schema covers limit and page. The openWorldHint annotation covers the incompleteness caveat. The description is complete enough for an agent to invoke the tool correctly.

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 58%, so the description carries meaningful weight. It explains the semantics of many filters in natural language (e.g., 'bajó de precio', 'sólo oportunidades', 'sin deuda ni choque declarados', 'publicados en los últimos N días') and adds the deduplication and automatic name resolution behavior. Some parameters like page and sort are not described in the description, but the schema covers those adequately. The description compensates well for the 42% gap.

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 opens with a specific verb ('Busca') and a precise resource ('autos usados en todo Uruguay'), then enumerates the aggregated sources and the deduplication behavior. It clearly distinguishes this tool from siblings like find_car_opportunities (which focuses on opportunities) and get_car (which likely retrieves a single car).

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 implies usage by listing all filter dimensions and noting that model requires brand ('requiere brand' in schema). It doesn't explicitly name sibling alternatives or state when not to use it, but the exhaustive filter list and the 'un mismo auto en varias fuentes aparece una vez' note give strong context. The openWorldHint annotation also signals that results may be incomplete, which is useful usage guidance.

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