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

Annotations already mark the operation as read-only and non-destructive. The description adds behavior beyond that: it charges $0.25 via x402, uses only public federal data, and produces a combined output of specs, recall count, fuel estimate, and a verdict, making side effects and cost transparent. No contradiction with 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?

A single dense sentence that front-loads the purpose, then lists inputs, outputs, data source, and pricing in order of importance. Every clause carries information; there is no fluff. The structure aids quick scanning by an agent.

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 3-param read-only tool with no output schema, the description lists all input semantics and the expected output components (decoded specs, recall count, fuel cost, and buy/caution/walk verdict with reasoning), plus cost and data-source context. It is sufficient for an agent to decide to call and interpret the result, though it stops short of detailing response shape or error conditions.

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?

All three parameters already have descriptions in the schema (17-char VIN, odometer miles, asking price USD), so baseline is 3. The description merely restates them ('Given vin, asking price and miles') without adding units, formats, or constraints beyond the schema. It is adequate but not additive.

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 opens with 'Used-car deal check verdict', naming the specific purpose, then enumerates inputs (vin, asking price, miles) and a distinctive deliverable (buy/caution/walk verdict with reasoning). This distinguishes it from sibling vehicle tools like vehicle_report and vehicle_vin, which focus on data rather than an evaluative verdict.

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 clearly states the trigger condition: when you have a VIN, asking price, and miles and want a deal verdict. It also notes the $0.25 cost and public-data basis, which helps an agent decide whether to invoke it. However, it does not explicitly compare against sibling alternatives such as vehicle_report or vehicle_fuel_economy, so exclusions are left to inference.

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