holiday_is_holiday

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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is known. The description adds the data source ('official Cabinet Office data'), which is useful context, but it does not describe the return format, error behavior, or timezone assumptions. With annotations covering the main safety traits, this is acceptable but not rich.

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?

A single, front-loaded sentence with no filler. Every word contributes: it states the action, the input, the output categories, and the authoritative data source.

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 one-parameter classifier with good annotations and no output schema, the description is mostly complete: it explains what the tool does and its output categories. It could mention edge cases (e.g., holiday substitutions prior to 1973, timezone behavior), but these are not essential for a basic classification tool.

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 fully describes the 'date' parameter format (YYYY-MM-DD), so baseline is 3. The description adds the meaning 'Japanese calendar date,' which implies the date is interpreted in the Japanese calendar/timezone—a semantic clarification not present in the schema.

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 a specific action: classify a date. It names the resource (Japanese calendar date) and the output categories (public holiday, weekend, business day). This distinguishes it from sibling tools like holiday_list (which lists holidays) and holiday_add_business_days (which adds 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 usage is implied by the description—you use this when you need to classify a single date. However, there is no explicit guidance on when to choose this over related tools like holiday_list or the business-day helpers, nor any mention of alternatives or exclusions.

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