list_holidaysList all Japanese national holidays and substitute holidays for a year, based on the National Holidays Act and verified against the Cabinet Office CSV. Each holiday has name (descriptive) and official_name (as written by the Cabinet Office). / その年の国民の祝日・休日（振替休日・国民の休日を含む）の一覧。name は内容がわかる名前、official_name は内閣府の表記。
| Name | Required | Description | Default |
|---|---|---|---|
| year | Yes | Year (1980-2099) / 年 |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the read-only/idempotent/closed-world profile, and the description adds real value on top: the data provenance (Cabinet Office CSV), the inclusion of substitute holidays and citizens' holidays, and the distinction between the two returned name fields. It does not discuss limits or edge cases like years outside the supported range.
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?
Purpose and scope are front-loaded in the first sentence, with field semantics following. The bilingual duplication doubles the length, but each half is tight and no sentence is wasted.
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?
With no output schema, the description usefully explains the two result fields (name, official_name), which an agent would otherwise have to guess. It still leaves the date representation of each holiday unstated, a minor gap for a simple read tool whose annotations already cover safety.
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 the single `year` parameter already documents its 1980-2099 bounds in the schema. The description's 'for a year' adds no format or syntax detail beyond that, so the schema is doing the heavy lifting.
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 and resource ('List all Japanese national holidays and substitute holidays for a year') and even grounds it in the National Holidays Act and Cabinet Office CSV. It is unambiguous against the business-day and postal-code siblings, though it never explicitly names or contrasts an alternative tool.
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 only implied: an agent can infer this is the tool for retrieving a year's holiday calendar, but there is no statement of when to prefer it over check_business_day or adjust_to_business_day, and no exclusions or prerequisites are given.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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