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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is clear. The description adds useful behavioral context by listing the exact fields returned and the scope of supported vehicles (all US vehicles including motorcycles and trailers).

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 efficient and front-loaded: it states the core function, then lists outputs, then gives query examples, then scope. Every sentence adds useful information, and the example phrases are practical for an agent matching user intent.

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 tool with one well-documented parameter, strong annotations, and no output schema, the description is complete: it explains what the tool returns, the vehicle types covered, and the user phrasings that should trigger it. No critical selection or invocation information is missing.

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 already fully documents the single 'vin' parameter, including its 17-character format. The description adds no additional parameter-level semantics beyond restating 'VIN', so the baseline score of 3 is appropriate given 100% schema coverage.

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 states a specific action ('Decode a VIN') and resource, and enumerates the returned vehicle attributes. It does not explicitly distinguish itself from the sibling 'vehicle_recalls' tool, though the specifications-focused output makes the difference mostly implicit.

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 provides concrete example queries and says to use it for 'any VIN lookup', giving an agent clear trigger phrases. However, it does not state when not to use it, such as when the user is asking about recalls rather than vehicle specifications.

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