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

With no annotations, the description carries the full burden and does so well: it discloses determinism ('Same day → same answer'), deployment properties (public, local, no API key), the output skeleton (first line time atom, then fold year, tone, sky marks), and mandated conversational behavior (always surface the fold-year line, ask what they lived that year). It even flags the preview-vs-prediction distinction. Only error/pagination class behaviors are unaddressed, which is minor for a local deterministic lookup.

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?

Purpose is front-loaded in the first sentence, which is good, but the description then mixes registers — determinism warning, a long bilingual trigger list, cryptic output formatting jargon ('#be time atom', 'keep 干支 in Chinese'), deployment notes, and a slogan — in a dense run-on. Every clause is arguably functional, but the presentation is cluttered rather than crisp.

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, so the description must carry the return-value burden, and it does describe the output sequence and the fact that date marks are dated. Combined with the trigger list and determinism statement, an agent has enough to call and interpret the tool. It stops short of explaining how fold-year or sky-mark values should be read in edge cases.

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 description coverage is 100% for both parameters (month pattern, locale enum), so the schema already documents them fully. The description adds no format, default, or interpretation detail beyond what the schema states. Baseline 3 is appropriate.

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 it looks up a deterministic rules engine and then enumerates what the result contains (time atom, fold year, baseline tone, dated sky marks), which lets an agent infer this is a month-level rhythm/flow briefing. It does not explicitly distinguish itself from the sibling personal_month or time_fold, so the differentiation is only implicit. Clear verb-plus-resource, but not sibling-disambiguated.

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 supplies a rich trigger list in both Chinese and English (这个月势能怎么样, this month's rhythm, which days to publish, 做不做某事), which is strong when-to-use guidance. However, it offers no explicit when-not conditions and no routing advice toward the obviously overlapping siblings personal_month or sky_window, so the agent must infer boundaries.

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