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

No annotations are provided, so the description carries the full behavioral burden. It usefully discloses a conditional behavior — the region is only named 'when the prefix table is loaded' — but says nothing about what happens for an invalid plate, whether the check raises or returns a boolean, or how prefix/region lookup failures surface.

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 with no filler; the primary action (checking plate format) is front-loaded and the secondary behavior (region naming) follows it.

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 and no annotations, so the description must cover return semantics. It partially does (region name, conditionally), but omits what the validity result looks like and how failure is reported — a real gap for a validation tool.

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 schema already supplies the format example 'B 1234 XYZ' and a maxLength. The description adds no additional semantics about the plate string, 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 description gives a specific verb ('Checks the format') and a specific resource ('Indonesian vehicle plate'), plus the bonus behavior of naming the region from the prefix. It is clearly distinguishable from the nearest sibling validate_nik by resource, but it never names a sibling or scope boundary explicitly, so it stops short of a 5.

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 statement of when to use this tool, when not to, or which alternative (e.g. validate_nik) covers a different case. Usage is only inferable from the domain wording, not guided.

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