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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds only the shape of the returned records, which the output schema already provides, and says nothing about completeness of the list, ordering, or size — the traits that would actually matter beyond 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?

A single compact line with zero filler; the useful content (what the list yields) is front-loaded. It reads as a caption rather than a sentence, which is the source of its slight clarity loss, not its length.

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 an output schema present, the description needn't explain return values, and locale is fully documented in the schema, so nothing critical is missing. Still, for a discovery tool that gates the other license-plate siblings, it gives no hint of list size, pagination, or how to proceed after listing.

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?

Schema description coverage is 100% and the locale enum documents its own behavior (answer and card language, fallback to app language) more thoroughly than the description does. The description mentions no parameters at all, so 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?

The fragment 'Countries whose license plates are available' conveys that this enumerates the supported country set and names the returned fields (code, region count, example plate). However, it never uses an explicit verb and never contrasts itself with the singular siblings get_license_plate_country / check_license_plate, so the agent must infer that this is the 'list all supported' variant.

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?

There is no when-to-use guidance, no exclusion, and no mention of the closely named alternatives (get_license_plate_country, check_license_plate, get_license_plate_image). The agent is left to deduce the discovery-then-detail workflow from the name alone.

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