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

Annotations already cover the safety profile (readOnly, idempotent, openWorld), so the bar is lower. The description still adds genuinely useful context beyond the structured fields: the result shape (5-digit codes with Japanese and English names), the upstream dataset identifier XIT002, and the required MLIT credit/attribution obligation.

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?

Front-loaded as a question that frames the purpose, followed by input format and output description. Slightly long with the trailing 'and other Japanese public data' / attribution clauses, but every sentence carries relevant information 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?

The tool is simple (one parameter, no nesting), an output schema exists so return values need no further explanation, and the description still supplies dataset provenance and attribution requirements. Nothing an agent needs to invoke it correctly is missing.

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 coverage is 100% and the single parameter already documents the accepted formats (code 01-47 or name such as Tokyo/東京都). The description restates the same input options without adding format, validation, or edge-case detail, so the baseline of 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?

States a specific verb and resource — retrieving the MLIT-listed municipality codes and names for a given Japanese prefecture — and names the source dataset (XIT002). It also distinguishes itself from the sibling realestate_prices_by_municipality by identifying itself as the join key for that tool.

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?

Tells the agent the required input format (prefecture code 01-47 or name) and implicitly frames this as the lookup step preceding realestate_prices_by_municipality. There is no explicit when-not guidance, but the routing context is clear for a single-purpose lookup tool.

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