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

Annotations cover readOnlyHint/openWorldHint, and the description adds genuinely new behavioral context the annotations lack: per-record credit cost with a minimum, and the best-effort nature of Autotrader/Cars.com coverage. Pagination interaction with cost is implied but rate limits or result-cap behavior aren't spelled out.

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 sentences, zero waste, front-loaded with the search scope before the caveats. Coverage limitation, cost constraint, and sibling routing each appear once and earn their place.

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 22-param, zero-required search tool with an output schema, readOnly annotations, and full schema descriptions, the description supplies the missing pieces an agent needs — data coverage caveats, cost model, and filter-discovery routing — without duplicating structured fields.

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 100%, so the schema already documents all 22 params and the baseline would be 3. The description adds semantic value the schema omits: the page_size / credit-cost tradeoff ('keep page_size to what you need'), which directly shapes how an agent sets that parameter.

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?

Opens with a specific verb+resource ('Search the used-vehicle listings dataset') and enumerates the filterable dimensions (year, make, model, trim, mileage, price, seller, location), so an agent knows exactly what surface this tool exposes. It also names the facets sibling for filter discovery, separating it from datasets_vehicle_listings_item and datasets_vehicle_listings_price_history.

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 routes the agent to datasets_vehicle_listings_facets to inspect available filters, and conditions page_size on cost. There is no stated 'when-not-to-use' (e.g. use item for a single listing by id), but the context for calling it is clear.

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