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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, openWorldHint, destructiveHint=false), and the description adds genuinely non-redundant behavior: look-alike letter normalization and the explicit privacy boundary that it never identifies the owner or the vehicle's location. It does not address rate limits or data sourcing, but the added behavioral detail is meaningful.

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?

Three sentences, front-loaded with the core action and its result, followed by the type override and the privacy disclaimer. The final 'Use it to check a specific plate number' sentence partly restates the opener, which is mild redundancy but serves as a routing hint.

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, return details need not be explained, and all five parameters are fully described in the schema. The description supplies purpose, normalization behavior, privacy boundaries and usage, leaving it essentially complete for an agent to call correctly.

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%, so the schema already documents country, number, region, locale and type in detail, including the enum for locale. The description only echoes the normalization note and the type-override behavior, adding marginal meaning beyond structured fields. Baseline 3 is appropriate.

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 (validate) plus resource (plate number), and adds the concrete output (which region the code belongs to). It also declares scope boundaries ('check a specific plate number'). It does not explicitly name a sibling such as get_license_plate_country or get_license_plate_image, so the differentiation is implied rather than stated.

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?

Gives a clear usage directive ('Use it to check a specific plate number') and explains that passing type checks against a specific plate type's format. That is actionable context, but there are no exclusions and no alternatives named for cases where another sibling tool is the right choice.

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