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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety behavior is covered. The description adds that the full, complete set of definitions is returned (全定義) along with facility counts, which is mild but real added value; it says nothing about result size or caching.

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 compact sentence that front-loads the action and immediately lists the payload contents. Nothing is redundant and nothing could be trimmed without losing 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?

There is no output schema, but the description compensates by naming the four fields each entry carries (id, label, target age, facility count). For a zero-parameter read-only listing tool, that is nearly everything an agent needs before calling it.

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?

This tool takes zero parameters, so the baseline of 4 applies. There are no arguments whose semantics need explaining, and the description correctly spends no space on input.

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 (返します/returns) and resource (子連れ条件の全定義), and even enumerates the returned fields (id・ラベル・対象年齢・該当施設数). It is unmistakably a reference-list tool, though it never explicitly contrasts itself with the sibling list_areas.

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?

「検索に使える」 implies the returned condition ids feed into search_hotels, which is useful usage framing. However, there is no explicit statement of when to call this versus search_hotels or list_areas, and no prerequisites or ordering guidance.

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