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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and a closed-world scope, so the safety profile is fully covered. The description adds one genuine behavioral fact beyond that — only "active" codes are returned — plus the shape of a sample entry, but says nothing about how many codes exist or the ordering of the result.

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 front-loaded sentence with the resource named first and the examples as a trailing parenthetical. Every clause earns its place and nothing is padded.

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?

For a zero-argument, no-output-schema listing tool, the description gives enough to call it correctly and to know what the returned codes mean. The only mild gap is the absence of any hint about result size or whether entries include province names alongside codes.

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 takes no parameters, so there is no parameter meaning to convey and the baseline of 4 applies. The description does not waste space restating schema detail, which is appropriate given the empty schema.

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 pairs a specific verb ("List") with a specific resource ("active Indonesian vehicle plate codes") and clarifies the domain with concrete examples (B for Jakarta, DK for Bali), so an agent knows exactly what comes back. It does not explicitly contrast with the sibling plates_get, which would be the natural lookup-by-code alternative, so it stops just short of 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 explicit when-to-use or when-not-to-use statement and no named alternative, though the implicit usage (browse the full set of plate codes before calling plates_get for details) is easy to infer. For a zero-parameter listing tool the guidance need is small, but nothing in the text routes the agent between plates_list and plates_get.

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