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

With no annotations, the description must carry the burden; 'FREE' usefully signals no billing/quota cost and 'short-term' bounds the forecast horizon. It omits whether an API key or auth is needed, what happens for unknown prefectures, and what the response contains.

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?

One tightly packed sentence with the cost signal front-loaded and the scope immediately after. Nothing is redundant.

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?

For a no-annotation, no-output-schema tool of this simplicity, this is close to sufficient, but the agent still gets no hint about return fields, time granularity (today/tomorrow), or language of the results.

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% and 'prefecture' is a bare string, but the description supplies both the meaning (a Japanese prefecture) and the default (Tokyo). That is the essential semantic an agent needs for the single parameter.

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?

Names a specific verb+resource: JMA short-term weather forecast scoped to a single prefecture. The scope ('for a prefecture') implicitly separates it from batch_forecast, but it never names or contrasts with either sibling explicitly.

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?

States a default (Tokyo) which tells the agent the parameter is optional, and 'for a prefecture' implies single-location use. It never says when to prefer batch_forecast or overview, nor when this tool should be avoided.

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