2日付間の営業日数

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

Annotations already declare readOnlyHint=true, so the safe-read nature is covered. The description adds meaningful behavior by specifying both endpoints are included and enforcing the start<=end constraint. It does not detail error handling or return type, but 'count' reasonably implies an integer.

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, direct sentence that immediately states the core action and boundary conditions. There is no filler, and it is optimally front-loaded.

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 two-parameter read-only tool with full schema coverage and clear annotations, the description is complete. It conveys the inclusive date range, the ordering requirement, and that the result is a business-day count, so no output schema is necessary.

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 100% and both parameters already have descriptions and format patterns (YYYY-MM-DD). The tool description adds no parameter-specific information beyond what the schema provides, so the baseline of 3 is appropriate.

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 uses a specific verb 'カウントします' (counts) with a clear resource: business days between start and end dates. It distinguishes itself from sibling tools like jp_is_business_day and jp_add_business_days by conveying a date-range counting operation, and it explicitly notes inclusive boundaries.

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 clear context for use: it counts inclusive business days and states the precondition that the start date must be before or equal to the end date. It does not explicitly reference alternative sibling tools or when-not-to-use scenarios, but the operation is sufficiently well-defined.

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