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

Annotations already declare read-only, idempotent and non-destructive behavior, so the bar is lower. The description adds real value beyond them: results are computed from actual astronomical positions, the supported date window is 1901–2099, and the client's shared location is used as a default for city/timezone.

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?

The resource and its output contents are front-loaded before the query examples and constraints, so the important material comes first. The single sentence is long and the query-phrase list is somewhat repetitive, but those phrases do earn their place as retrieval anchors.

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, the description carries the burden of describing return values, and it does so thoroughly: lunar date, ganzhi pillars, day officer, solar terms, zodiac, phase colour and moon phases. Coverage of defaults and date limits is adequate; only cross-tool routing is missing.

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%, so the baseline is 3; the description nonetheless adds meaning by pinning the 1901–2099 date range and clarifying that omitting city/timezone falls back to the user's shared location. It does not expand on the include_planetary_hours flag beyond the schema's default note.

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 a specific resource (a day's Chinese almanac / tong shu / 黄历 Daily Alignment card) and enumerates its contents, so an agent knows exactly what it produces. It does not explicitly distinguish itself from siblings such as convert_lunar_date or get_four_pillars, which overlap on lunar date and ganzhi output.

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 gives concrete trigger phrasings in English and Chinese ('today's almanac', '今天农历') and states the location fallback when no city is supplied, which is clear usage context. It stops short of stating when to prefer convert_lunar_date or get_almanac_month instead, so there are no explicit exclusions.

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