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

Annotations already declare readOnly, idempotent, and non-open-world, so the safety profile is covered. The description adds genuinely new behavioral context beyond that: results are 'source-cited' and the agent is forbidden from extrapolating fitment. That is meaningful guidance not present in structured fields.

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 sentences, no padding, with the core purpose front-loaded and the constraint immediately following. Every clause earns its 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 read-only lookup with no output schema and fully documented parameters, the description covers purpose, filtering, and the key epistemic constraint. It does not describe the shape of a fitment record (fields, citation format), but with no output schema that is 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 100%, so all three parameters are already documented, including that category and vehicle_slug come from list_vehicles. The description only adds that the filters are optional, which the schema's required list already shows. Baseline 3 applies.

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 ('Find') and resource ('source-cited fitment records') scoped to one vehicle, which clearly separates it from get_part (single part) and list_vehicles (vehicle enumeration). It stops short of naming those siblings or excluding them explicitly, so it is clear but not fully differentiated.

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 tells the agent the two optional filters (category, part-number/name search), which implies usage, and adds the constraint 'Never infer fitment beyond these records.' However, it never says when to reach for this tool instead of get_part or list_vehicles, leaving the routing decision to inference.

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