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

Beyond the readOnlyHint/idempotentHint annotations, the description discloses important behavioral details: the result contains provenance, freshness, VIN photo, market comparison, full details, and the inquiry contract. It also explains the 'not found' behavior as likely indicating the vehicle sold, which is useful operational context not present in the 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 compact and every sentence earns its place: purpose, parameter guidance, expected result contents, and failure handling. It is front-loaded with the core action and immediately gives the critical instruction about the id.

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 single-parameter read-only retrieval tool with an output schema present, the description covers all necessary operational aspects: how to identify the target, what the response contains, and how to interpret failure. No critical 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?

Although the schema already covers the `id` parameter at 100%, the description adds substantial meaning: the id is dealer-qualified, must be passed unchanged, and must not be replaced by a VIN because one VIN can map to multiple listings at different prices. This is valuable semantic guidance beyond the bare schema text.

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 ('Fetch') and a specific resource ('the exact vehicle listing selected from search_inventory'), making the tool's purpose immediately clear. It also distinguishes this tool from siblings like search_inventory and get_market_prices by focusing on a single already-selected listing.

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 says to use this when retrieving a vehicle selected from search_inventory and instructs the agent to always pass the `id` unchanged. It also warns against substituting the VIN, explains why, and tells the agent to search again if 'not found' occurs, providing clear when-to-use and when-not-to-use guidance.

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