list_prefectures

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 useful behavioral details beyond annotations: the exact fiscal-year range, that the tool is intended as a first call, and what the response contains, including the national weighted average.

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?

The description is compact and front-loaded with the core purpose, followed by a clear usage directive and a concise return summary. Every sentence adds value; there is no filler or repetition of structured information.

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?

Given zero parameters, a present output schema, and rich annotations, the description is complete. It tells the agent what the tool returns, when to call it, and the scope of data covered, leaving no important gap for correct invocation.

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 has zero parameters and an empty input schema, so there is nothing for the description to explain about parameters. The schema coverage is 100% trivially, and the description correctly focuses on return content rather than parameter semantics.

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 states a specific verb and resource: 'List all 47 prefectures with romaji aliases and the available fiscal years.' This clearly distinguishes it from the sibling tools, which retrieve minimum-wage data rather than enumerate prefectures and fiscal coverage.

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?

It gives explicit context: 'Call this first if unsure which prefecture names are valid, or to discover the historical coverage.' It does not explicitly enumerate when not to use it or name alternatives, but the usage context is clear enough for an agent to select it as a discovery/prerequisite tool.

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