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

With no annotations, the description carries the full disclosure burden, and it discloses the tool's central behavioral trap: returned rates are effective-date-dependent and vary per prefecture, so a stale assumption would yield wrong results. It also sets data-coverage expectations ("History runs back to FY2002") for time-travel queries. The only unaddressed trait is return shape, partly mitigated by the "Hourly" qualifier.

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?

Three sentences, each earning its place: purpose, temporal usage warning, and data coverage. The most important caveat (date sensitivity) is front-loaded immediately after the purpose statement. No filler, no restatement of schema fields.

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 straightforward lookup with 100% parameter documentation and no output schema, the description covers purpose, the revision-timing trap, and historical depth — sufficient for correct invocation. Minor gaps are the unstated read-only/safety profile (no annotations) and no return-value description, both low-risk given the "get_" prefix and simple hourly-rate nature.

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%, so each parameter is already documented with format and default behavior (e.g., date defaults to the currently enforced rate; prefecture accepts English, Japanese, or JIS code). The description enriches the date parameter by explaining why it matters and ties the history parameter to the FY2002 range, but the schema does the heavy lifting — baseline 3 with modest added meaning.

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 opening sentence names a specific resource — "Hourly 地域別最低賃金 for a prefecture" — with a clear lookup verb and scope, and the title's "(指定日時点)" adds the as-of-date qualifier. It is easily distinguished from siblings like get_insurance_rates and get_statute_text by domain, though it never names an alternative explicitly.

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 gives concrete operational guidance: "pass one when checking a past payroll rather than assuming the current rate applied," backed by the reason (revisions take effect prefecture by prefecture from October on different days). This tells an agent exactly when the optional date is effectively required, though it does not name alternative tools or state exclusion conditions.

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