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

With no annotations, the description carries full responsibility for behavioral disclosure. It does mention that the return value is a 'フォーマットされた文字列' (formatted string), which is helpful. However, it does not disclose potential errors, units, or any other behavioral nuances. For a simple read operation, this is adequate but minimal.

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 extremely concise, with a one-sentence purpose followed by well-structured Args and Returns sections. Every element is necessary and directly serves the user's understanding, with no redundancy.

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 simple tool with one parameter and no siblings, the description covers the essential aspects: purpose, parameter semantics, and return format. It falls short only on minor details like units (Celsius vs Fahrenheit) or error behavior, but these are not critical for understanding the core functionality.

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?

The schema provides no description for the 'city' parameter (0% coverage), but the description's Args section explicitly explains it as '都市名' (city name) with examples (Tokyo, London, New York). This fully compensates for the schema gap and adds practical meaning.

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 clearly states the tool's function: '指定された都市の現在の天気を取得します' (Gets the current weather for the specified city). This uses a specific verb (get) and resource (current weather for a city), leaving no ambiguity about what the tool does.

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 provides no guidance on when to use this tool versus alternatives, nor does it mention any prerequisites or context. Since there are no sibling tools, it could have simply stated the use case (e.g., 'Use this to check current conditions'), but it remains implicit at best.

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