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

Annotations cover the safety profile (readOnly, non-destructive, open-world), and the description adds real behavioral context: the response reports percentile/median/typical range with sample size and mileage-matching, zip selects local vs national, and the URL is parsed rather than fetched. The disclosure that the link is never fetched is exactly the kind of non-obvious behavior an agent needs; only the return-value detail overlaps the existing output schema.

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-loaded with the core instruction, then triggers, then examples, then the sibling hand-off. It is longish, but the examples and the explicit alternative earn their place; nothing is padding.

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?

With annotations carrying safety, an output schema carrying return shape, and a schema documenting most params, the description fills the remaining gaps: when to call, what the user must provide, local-vs-national behavior, and the sibling it must not be confused with. Nothing material is missing.

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 67%, near the baseline where the schema does most of the work. The description reinforces the two highest-leverage inputs ('pass the whole sentence as query, plus the listing url if they gave one') but supplies no format or syntax meaning beyond what the schema fields already state (zip→local, mileage→biggest driver are both documented in the schema).

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 and resource ('tell whether the asking price on ONE specific car is a good deal'), and explicitly distinguishes itself from demand.find_vehicle. An agent can route between pricing a found car and choosing a car without opening either schema.

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 explicit trigger conditions ('whenever someone is looking at a particular vehicle and asks if the price is fair, high, low'), three concrete example utterances, and names the alternative with the condition that selects it ('Use demand.find_vehicle instead when the user is still choosing which car to buy'). This is close to ideal routing guidance.

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