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

The annotations already declare readOnly, idempotent, openWorld and non-destructive, and the description adds material context: source RDW, cost of 0.001 USDC via x402 or one Factline credit, and five free paid-tool calls per day. That pricing and auth detail matters for an agent deciding whether to call, and the annotations do not contradict it.

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 trigger, output fields, scope, input, source and cost are packed into three sentences, and the trigger leads with no preamble. Every clause carries information an agent needs, including the free-tier detail that affects call decisions.

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?

There is no output schema, so the description compensates by naming the returned fields and status bands. Together with the source, cost model and free tier, it is complete enough for an agent to call it correctly on the first attempt.

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 tool has only one parameter, and schema coverage is 100% with an example format (GT-722-F). 'Input: Dutch licence plate' restates the schema rather than adding syntax or validation detail, 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 states a specific verb (look up expiry and validity) and resource (a Dutch car's APK/MOT), and lists the exact outputs: expiry date, days left, status band, insurance and open-recall flags. This clearly separates it from siblings such as nl_vehicle_report and buy_full_vehicle_report.

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 gives an explicit trigger, 'Use when the user asks when a Dutch car's APK expires or whether it is still valid,' and adds that it is cheap enough to run daily for a fleet. It does not name alternatives or say when to use a sibling instead, so it falls short of a 5.

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