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

With no annotations provided, the description carries the full burden of explaining behavior. It discloses the comparison scope and one conditional ('where a press kit is on file'), but it does not describe the output format, how missing data is handled, or what happens when one vehicle ID is invalid. This is adequate but not rich.

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 a single sentence that packs substantive detail efficiently. The opening phrase 'Two model years side by side' is reasonably front-loaded, though the marketing phrasing 'the figures that decide most purchases' adds little functional value and could be trimmed.

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 comparison tool with no output schema and no annotations, the description should explain the result shape or behavior more fully. It covers the evaluated dimensions well, but an agent is left without an explicit idea of what the returned comparison looks like or how edge cases (e.g., missing press kit, invalid ID) are presented.

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%, with clear descriptions for both parameters ('First vehicle id' and 'Second vehicle id'). The description adds the context that these are model years or vehicles being compared, but it provides no additional semantic detail beyond what the schema already states, so the baseline of 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?

The description clearly identifies the tool's function as presenting two vehicles side by side across key purchasing figures such as fuel economy, EV range, safety grade, recalls, complaints, crash rating, and starting price. The resource (vehicles/model years) is evident, and the listed dimensions distinguish it from sibling tools like get_vehicle or search_vehicles, though it never uses an explicit verb like 'compares'.

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: an agent would use this when needing a side-by-side comparison of two vehicles. However, the description does not explicitly state when to choose this over alternatives such as get_vehicle for a single vehicle, and it offers no exclusions or conditions beyond the press-kit caveat for starting price.

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