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

Beyond readOnly/destructive annotations, it discloses the key behavioral traits: exact astronomical instant at 15-degree longitude steps, the solar year opening at Li Chun with the last two terms in the following January, and dual UTC/UTC+8 returns. This is precisely the kind of non-obvious behavior an agent needs.

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, front-loaded with the core function and then adding the critical timezone and boundary quirks. No filler or redundant restatement.

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 tool with no output schema, the description does a good job of covering the return concept (all 24 instants, UTC and UTC+8) and the main boundary edge case. It stops short of specifying exact field names or value formats, which would make it fully self-sufficient, but the invocation-relevant context is present.

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?

The input schema already documents all three parameters with descriptions at 100% coverage, so the description need not re-explain lang or compact. It reinforces the solar-year meaning of `year`, but that information is already present in the schema, so no substantial parameter semantics are added.

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?

Description opens with a specific verb and object: 'Return all 24 solar terms of a year as astronomical instants rather than dates.' This clearly distinguishes it from the day-date and monthly sibling tools, and the solar-year/Li Chun detail defines its scope unambiguously.

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 provides concrete use contexts (calendar apps, festival scheduling, BaZi boundary placement) and makes the solar-year vs Gregorian-year scope explicit, so an agent can infer when this tool applies. It does not explicitly name sibling alternatives or state when not to use them, so it stops short of full routing guidance.

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