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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, so the description's job is to add context, which it does: it names the authoritative data source (RDW), enumerates the data classes returned including sensitive ones (insured status, open recall, odometer verdict), and discloses a cost of 20 credits. It does not cover failure behavior for an unregistered or malformed plate, but the added disclosure is substantial.

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 sentence, front-loaded with the action and the authority, then a dense field list and the credit cost at the end. Every clause carries information; the mid-sentence attribute enumeration is long but justified because no output schema exists.

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?

With no output schema, the field enumeration effectively documents the return payload, and the credit cost flags a paid call — both important for a one-parameter tool. Missing only edge-case behavior (invalid plate handling, partial data) to be fully complete.

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?

Only one parameter, and the schema already documents it at 100% coverage with an example (XN-097-Z). The description contributes the Dutch term 'kenteken' and reinforces that the input is a Dutch plate, but adds no format or normalization rules beyond the schema, so the baseline 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?

States a specific verb and resource: number plate (kenteken) lookup against the Dutch RDW authority, followed by an enumeration of the returned attributes. It is clearly distinguishable from most siblings, though the near-neighbour vin_decode is not named as the alternative for non-plate vehicle identification.

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 is implied by 'lookup from the Dutch vehicle authority RDW' — you call it when you have a Dutch plate. There is no explicit when-to-use/when-not guidance and no mention of vin_decode as the alternative for VINs or non-Dutch vehicles, leaving routing to inference.

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