jp_count_days

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

With no annotations, the description carries the full burden. It discloses that it counts both calendar and business days, excludes Japanese holidays from business days, and is order-insensitive. But it does not specify whether the count is inclusive/exclusive of the endpoints or what the return structure looks like, leaving ambiguity for the agent.

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 sentence that front-loads the main purpose and then adds the key behavior (exclusion of Japanese holidays) and the order-insensitivity note. Every word earned its place, with no fluff 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?

The tool is simple with fully described parameters, but there is no output schema. The description does not explain the return value format or edge cases (e.g., invalid dates, inclusivity). Given that the description must compensate for the missing output schema, it is not fully complete, though it covers the core functionality adequately.

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 already provides 100% coverage by naming and describing both parameters (start and end with YYYY-MM-DD format). The description adds extra semantic value by stating the order does not matter, which is not evident from the schema alone. This justifies a score above the baseline of 3.

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 ('Count') and identifies the exact resource ('calendar days and business days between two dates'). It also clarifies a distinguishing feature ('Japanese holidays excluded from business days'), which differentiates it from sibling tools like jp_check_date or jp_shift_days.

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 clearly implies when to use the tool: whenever an agent needs to count days between two dates. It also provides a useful usage note that the date order does not matter. However, it does not explicitly compare to alternatives or state exclusion criteria, so it is not a perfect 5.

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