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

With only readOnlyHint=true in annotations, the description carries real behavioral weight: it enumerates the exact return vocabulary and commits to a 'never guesses when data is missing' policy, which tells the agent how to treat the `unknown` case. It omits latency, caching, or data-coverage limits, but the tri-state contract is the important disclosure and it is present.

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?

Two tight sentences with no filler, and the most decision-relevant fact (the tri-state output) is front-loaded. The tradeoff is that the opening sentence leads with return values rather than a purpose statement, so it is efficient rather than optimally structured.

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 lookup with no output schema, the description usefully documents the return values, which is the main gap such a tool usually has. It remains incomplete on the four undocumented parameters and on how it differs from the overlapping `tire_fitment` sibling.

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% across four required parameters, so the description must compensate and does not. In particular `product_url_or_sku` accepts two different input forms and neither the schema nor the description explains the expected format.

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 states the three-valued result (fits / does_not_fit / unknown) and the data source (manufacturer application data), making the tool's job clear when read with the title. It does not distinguish itself from the sibling `tire_fitment`, which appears to be an overlapping fitment tool.

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?

No when-to-use guidance and no alternatives named. With a sibling called `tire_fitment` covering similar ground and `find_parts_for_vehicle` in the mix, the agent gets no help deciding which fitment tool to call for a given query.

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