空き家率統計

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

Annotations already declare readOnlyHint=true, making the read-only nature clear. The description adds context about the output (types, national comparison) but no additional behavioral traits (e.g., caching, rate limits, authorization needs).

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 two sentences (English and Japanese), front-loaded with key information. Every word earns its place; no redundancy or fluff.

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 the tool's simplicity (2 optional parameters, no output schema, annotations present), the description covers input behavior and output components. However, it could specify the output structure (e.g., field names) for greater completeness, especially since no output schema exists.

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% with both parameters described. The prefecture parameter specifies support for multiple name formats (and name/English/ISO), and the area parameter includes an example and explains omission behavior (returns full prefecture data). This adds useful meaning beyond the schema type.

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 clearly states it returns vacancy rate statistics by municipality, broken down by type (total vacant, for-rent, for-sale, other), and compares to national average. This differentiates it from siblings that focus on analysis, forecasting, or risk assessment.

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?

The description implies usage for obtaining vacancy statistics but does not explicitly state when to use this tool versus alternatives like compare_prefectures or get_real_estate_macro_snapshot. No when-not or exclusion criteria are provided.

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