緯度経度から近傍住所を検索(逆ジオコーディング)

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

With no annotations, the description carries full burden. It discloses precision limit (町丁目レベル), geohash limitation, approximate search nature, and potential missing candidates near prefecture boundaries. This goes beyond the schema and explains behavioral traits.

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, with the first sentence stating the core purpose and the second adding critical limitations. Every sentence earns its place; no 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?

The tool is simple with 3 well-documented params and no output schema. The description explains what it does, addresses precision, and limitations. It could explicitly state the return format (e.g., list of candidates), but '住所候補' implies multiple results, making it sufficiently complete for context.

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%, so baseline is 3. The description's precision limit explanation mirrors schema's precision parameter details, but adds no new meaning beyond the schema. The schema already fully documents lat, long, and precision.

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 '緯度経度から近傍の町丁目レベルの住所候補を検索する' (search nearby town/chome-level address candidates from lat/long), which is a specific verb+resource. It distinguishes from siblings by specifying reverse geocoding and precision limits, unlike forward geocoding tools like search_address.

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 explicitly notes this is not strict point-in-polygon geocoding ('点在ジオコーディング...ではない'), implying when not to use. It also mentions approximate nature and boundary-related miss risk, providing context for when to use it (when approximate reverse geocoding is acceptable). No explicit alternative tool names, but the exclusion is clear.

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