search-by-model

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is known. The description adds useful behavioral context by enumerating the exact return fields (tyre size, rim spec, PCD, CB, OEM/aftermarket) and clarifying the empty-data-array edge case, which is not an error.

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?

The description is three sentences with clear front-loading: purpose first, then return format, then edge-case clarification. Every sentence carries meaningful content with no redundancy.

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 tool with no output schema, the description sufficiently covers output fields and edge-case behavior. The detailed parameter schema complements it well. Minor omission is lack of pagination/limit info, but it's not a list endpoint.

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 descriptions provide 100% coverage with rich detail—examples, slugs, and cross-references to list tools. The tool description itself adds no extra param-level semantics beyond restating the inputs, so the baseline of 3 is appropriate.

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 uses a specific verb ('Look up') and resource ('wheel/tyre fitment specs'), and specifies exact inputs (make, model, year, region). It also declares itself 'the primary tool for fitment lookups,' distinguishing it from siblings like search-by-rim and search-by-tire.

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?

It explicitly positions the tool as the primary fitment lookup, implying it should be used when vehicle details are known. It does not explicitly name alternatives or when-not conditions, but the sibling context and the phrase 'primary tool' provide clear enough guidance.

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