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

No annotations are provided, so the description carries the full behavioral burden, yet it says nothing about what is returned, the unit of measure (raw person-nights vs an index), the time period or data freshness, or whether a missing prefecture errors. The word 'シグナル' in the name hints at a derived signal but is never explained, leaving the agent guessing about the response shape.

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 phrase with no filler, front-loading the source and then the metric. It is terse to the point of being a bare noun phrase, but nothing is wasted.

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?

With no annotations, no output schema, and an undocumented sole parameter, the description should do far more for a data-retrieval tool. It never establishes units, time coverage, or the format expected for 'prefecture', which are exactly the gaps structured fields do not fill here.

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?

There is one required parameter (prefecture) with 0% schema description coverage, and the description does not define its accepted format — Japanese prefecture name, romaji, or a code. The phrase '都道府県別' only confirms that the value selects a prefecture, which the parameter name already tells the agent.

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 names a specific metric (外国人延べ宿泊者数, total overnight stays by foreign visitors) at a specific granularity (都道府県別) and a named source (総務省統計局 都道府県データ基礎データ). That is a clear verb-less but unambiguous resource statement. It does not differentiate itself from siblings such as jp_facility_signal or jp_quality, which share the vague 'signal' suffix.

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?

There is no statement of when to use this tool versus the many jp_* siblings, and no indication of what question it answers (tourism demand? inbound trend?). The only implied usage comes from the metric name itself.

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