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

With no annotations, the description carries the burden of behavioral disclosure. It adds the useful detail 'サマータイム自動対応' (automatically supports daylight saving time), which is a behavioral trait. However, it does not disclose output format, timezone name validation, or error handling, so transparency is incomplete.

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, compact Japanese sentence with two clauses. It is front-loaded with the primary purpose and contains no filler. Every word adds value, making it highly concise.

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?

The tool is simple with three well-documented parameters, but there is no output schema and the description does not explain what the tool returns. The description covers the core function and DST support but lacks details about the output structure or customization options, making it minimally 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?

Schema description coverage is 100% (all three parameters have descriptions), so the baseline is 3. The description does not add parameter-specific meaning beyond what the schema already provides; it mentions 'major cities' but does not map this to the actual parameters.

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: '世界の主要都市の時差を即計算' (instantly calculate time differences between major world cities). This is a specific verb+resource that distinguishes it from sibling tools like timestamp-converter and date-calculator, though it doesn't explicitly mention converting a given datetime to multiple timezones.

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?

Usage is implied by the description: it is for calculating time differences between major cities. However, there are no explicit alternatives or exclusions mentioned. Given sibling tools like timestamp-converter could be confused, the lack of explicit 'when to use this instead' guidance keeps it at a middle score.

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