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

No annotations are supplied, so the description carries the full behavioral burden, and it discloses almost nothing: no time period covered, no units, no observation vs forecast distinction, no pagination or response shape, no auth or rate-limit notes. The only behavioral content is the implicit claim that results are per-prefecture and cover three weather metrics.

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?

It is one short phrase with zero padding, so there is nothing to trim. The trade-off is that the brevity comes from omission rather than compression: it is structured as a label rather than as a front-loaded statement of action and scope.

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 output schema and no annotations, the description is the only documentation an agent has, and it is insufficient for a data-retrieval tool: the time range, aggregation window, and return structure are all unknown. A caller could invoke it but could not predict or validate the result.

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 0% for the single required parameter, so the description must compensate. The phrase 都道府県別 does confirm the parameter's role as a prefecture scope, which is the minimum needed to use it. But it gives no expected format — Japanese name, romanized name, or JIS code — leaving a real risk of an invalid call.

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 the data source (気象庁 / JMA) and the resources covered (気温・降水量・日照時間) at prefecture granularity, so an agent can guess it retrieves weather data. However it is a bare noun phrase with no verb, and the term シグナル ("signal") is undefined, so what the tool actually does with that data (fetch raw observations, compute an index, return an alert) is left to inference rather than stated.

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 when-to-use guidance, no exclusions, and no reference to any alternative. The sibling list contains several other 'signal' tools (jp_tourism_signal, jp_facility_signal, jp_energy_price) but nothing in the description says how to choose between them or when this one is the right call.

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