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

With no annotations provided, the description must carry behavioral disclosure. It does disclose how unknown/unavailable IDs are handled ('listed in not_found'), which is useful. However, it does not state whether the operation is read-only, what happens if fewer than 2 or more than 5 IDs are provided, or any other limitations. The description adds some behavioral context but not enough to fully compensate for the absence of annotations.

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 two concise sentences with no filler. The primary purpose is front-loaded in the first sentence, and the behavioral note follows immediately. Every word 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?

Given the tool's simplicity (one parameter, no nested objects, no output schema) and no annotations, the description is mostly complete. It covers purpose, scale, key spec examples, and error handling. It could go further by describing the response shape or behavior for invalid vehicle count, but these are minor gaps for a straightforward comparison tool.

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?

The schema describes vehicle_ids only as an array of integers, with 0% description coverage. The description compensates by adding meaningful constraints: it indicates 2-5 vehicles are expected and explains that unknown IDs will appear in 'not_found'. This goes beyond the raw schema, although it does not detail ordering, uniqueness, or exact response structure.

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 and resource: 'Compare 2-5 vehicles side by side on key specs.' It clearly conveys what the tool does and the scope, though it does not explicitly name or differentiate from sibling tools like get_vehicle or search_vehicles. The '2-5 vehicles' phrasing implicitly separates it from single-vehicle fetching, but the distinction is not made explicit.

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 implies when to use the tool: when you need a side-by-side comparison of 2-5 vehicles. However, it does not explicitly state when not to use it or name alternatives such as get_vehicle for a single vehicle or search_vehicles for discovery. Alternatives are only available via the sibling-tools context, not in the description itself.

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