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

With no annotations, the description must carry the full behavioral burden. It discloses the cost ('Free') and the non-deterministic/interpretive nature of the output, which is genuinely useful context, but says nothing about output size, whether results are deterministic, or how the optional purpose input changes what is returned.

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?

Compact and front-loaded: the data payload is listed first, then a usage caveat and the cost note. Dense domain jargon is unavoidable here for almanac content, and no sentence is wasted.

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?

There is no output schema, and the description compensates by naming the categories of returned data, which is the key completeness gap for this tool. What is missing is any treatment of the purpose parameter's effect, otherwise an agent could call it correctly from this text.

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 only 33%: year and month have no schema descriptions and the description gives no format, range, or calendar convention guidance for them. More importantly, the purpose parameter is never mentioned in the description, so the agent gets no signal about how supplying a purpose alters the almanac output — the description does not compensate for the coverage gap.

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 specific resource (a month of Chinese almanac data) and enumerates its contents: day stems/branches, 建除 officers, Yellow/Black Path spirits, 28 mansions, suitable/unsuitable activities, solar terms. That is concrete enough to separate it from the chart-oriented siblings (bazi_chart, ziwei_chart), though the action verb is only implied by 'for a month'.

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?

'Use it to suggest when to begin something' gives an implied use case, and the caveat that results are not a guarantee of outcome sets expectations. There is no explicit when-not guidance and no alternatives named among the sibling tools, so the agent must infer routing on its own.

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