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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false, and destructiveHint=false, so the safety profile is fully covered elsewhere. The description adds genuinely useful provenance (内閣府公表データに基づきます), telling the agent the authority and likely update cadence of the result, but says nothing about behavior for out-of-range dates, dates before the data set begins, or the shape of the returned judgement.

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?

Two short, front-loaded sentences that put the core determination first and the data source second. The trailing input example is redundant with the schema example, which is the only wasted element.

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 one fully-documented parameter and complete safety annotations, the definition covers invocation adequately. However, there is no output schema, and 判定します leaves ambiguous whether the result is a bare boolean, a holiday name, or a structured object — a meaningful gap for a predicate 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?

Schema description coverage is 100% and the single parameter already documents the YYYY-MM-DD format with the same example. The description's input example merely repeats the schema example, adding no new syntax, timezone, or range constraints beyond what structured data provides.

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 states a specific verb (判定します) and resource (日本の祝日（国民の祝日・休日）), scoped to a single date, which implicitly separates it from list_holidays. It never names a sibling explicitly, so the differentiation is inferential rather than stated.

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 phrase 指定した日付 ('a specified date') and by the input example, which shows the single-date check pattern. There is no explicit when-to-use / when-not-to-use guidance and no mention of when to prefer list_holidays or business-day tools instead.

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