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

With no annotations and no output schema, the description carries the burden of explaining behavior. It does so by disclosing that the tool uses a fixed six-item basket across 81 cities and produces a monthly cost figure, which is meaningful behavioral transparency for a zero-parameter read-only comparison tool.

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 a single, dense sentence that front-loads the core action ('市をくらべる') and then efficiently supplies method, scope, and typical user intents. No wasted words or repetition.

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-parameter, no-output-schema tool, the description sufficiently covers what the tool does and when to use it. It could be more explicit about how results are presented (e.g., ranked list, all 81 cities), but the core decision-making context is complete.

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 tool has zero parameters, and the schema coverage is essentially complete. The description adds value by defining the basket contents and the unit of comparison (monthly cost), satisfying the baseline of 4 for parameter-free tools.

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 verb ('くらべる') and resource ('81市'), and explains the comparison method: applying a fixed basket of items (rent, rice, eggs, milk, bread, electricity) to compute monthly costs. This distinguishes it from sibling city/cost tools by clarifying it compares cities with an identical basket.

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 gives clear use cases: '引っ越すといくら変わる' and 'どの街が安い' consultations. It does not explicitly name alternative tools or when-not-to-use, so it falls short of a full 5, but the use context is strongly implied.

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