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

Annotations already declare readOnly, idempotent, closed-world and non-destructive, so the safety profile is covered. The description adds genuinely non-structured behavior: prefix matching ('or the start of one'), input normalization of dashes/spaces, minimum length, and a 25-result cap that tells the agent to narrow ambiguous queries. It stops short of describing error or empty-result behavior.

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 compact sentences: what it resolves, input constraints, and result cap. No filler, and the primary purpose is front-loaded before constraints.

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?

There is no output schema, and the description compensates by enumerating what comes back (part identity, engine fitment, supersession chain, 25-result cap). It is nearly complete for a single-parameter read tool; only the shape/ordering of the returned records is left unstated.

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% and the schema supplies an example, so baseline would be 3. The description goes further by explaining accepted format variations (dashes and spaces ignored), the 4-character floor, and that partial/prefix numbers are valid input — semantics an agent would otherwise have to guess.

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 (part number) plus the exact payload returned: which part it is, which engine it fits, and supersession info. The domain (Ford, Mopar, GM, aftermarket) makes it trivially distinguishable from siblings like lookup_vin and list_platforms.

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?

Usage context is implied by the purpose ('find which part...'), and there is useful input guidance (dashes/spaces ignored, minimum 4 characters, prefix allowed). However, no alternative is named and no when-not-to-use condition is given, even though lookup_vin is a plausibly confusable sibling for identification tasks.

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