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

Annotations already declare a safe read-only, closed-world operation, so the description adds genuine context beyond them: timezone (JST), precision (seconds plus minute-rounded values), and the provenance claim of being verified against the NAOJ 暦要項. It does not cover edge behavior such as supplying both year and start/end, or what is returned when a span crosses a year boundary.

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?

Five short sentences, each carrying a distinct fact (what is returned, precision, examples, input modes, trustworthiness), front-loaded with the returned value. No filler or repetition of the title.

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 and zero required parameters, the description should say what the default invocation returns and what shape the response takes; it says neither. Coverage of the input modes, timezone and precision is otherwise solid for a simple read-only lookup.

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?

Beyond the 67% schema coverage, the description contributes two facts the schema does not: the mutual exclusivity of the two modes (year vs. start+end) and a maximum span of 366 days, which the schema never states for start/end. It leaves the zero-required-parameter case (what happens with no arguments) unexplained.

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 the resource precisely: the date-times of the 24 solar terms' setsu-iri (節入り), with concrete examples (立春・春分・夏至・秋分・冬至) that anchor what a 'solar term time' means. It does not explicitly contrast itself with siblings such as get_sun_moon_times or get_moon_events, though the scope is distinct enough to infer the difference.

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?

It tells the agent how to scope a query ('year か、start と end') and implicitly when this tool applies (you want the clock time of a solar-term ingress). It never states when NOT to use it or names an alternative sibling for related calendrical queries, so usage is implied rather than guided.

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