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

Annotations already declare read-only, closed-world, and non-destructive behaviors, so the bar is lower. The description still adds real information: results are in Japan time, based on a representative point per prefecture rather than a precise location, and computed under the NAOJ '各地のこよみ' definition.

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 sentences, front-loaded with the full list of returned values, followed by scope and the astronomical reference standard. Each clause earns its place, with no filler.

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?

It covers inputs beyond the schema and states the definitional basis, but with no output schema it doesn't specify the return format (for example, 'HH:MM' strings), error behavior for out-of-range dates or unknown prefecture names, or how it differs from the overlapping moon sibling. The definition is adequate but leaves real gaps.

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%, with the date range and prefecture examples already documented in the schema. The description adds only the useful nuance that prefecture selection maps to a representative point (so results are approximate), which is a modest but genuine addition beyond 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 names the concrete resources returned (sunrise, sunset, moonrise, moonset, and culmination) and scopes them to a given date and prefecture, so the agent knows exactly what this tool produces. It does not distinguish itself from the sibling `get_moon_events`, which appears to cover overlapping moon data.

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 only implies usage ('specified date/prefecture, Japan time') and never states when to choose this tool over `get_moon_events` or `get_solar_term_times`. There are no exclusion rules and no prerequisites, leaving the agent to infer which of the overlapping tools to call.

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