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

With no annotations, the description carries the full burden and does disclose meaningful traits: deterministic (same day → same answer), local execution, no API key required, and a 'Preview ≠ prediction' caveat. It omits failure modes and rate/edge behavior, but goes well beyond restating the name.

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 and determinism are front-loaded, and most sentences carry distinct information (triggers, output sequence, constraints). It is dense and code-switches heavily, edging toward run-on, but little is genuinely 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?

With no output schema, the description usefully outlines the return structure (be time atom, east pillars, fold year, posture × west tightness, daily almanac), which an agent needs. It is fairly complete for a zero-required-param lookup tool, though error/edge behavior is unstated.

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%, so the schema already documents date, hour, and locale, including the Asia/Shanghai default and enum. The description adds only light context (hour yields the hour pillar), so 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?

States a specific resource and verb: a deterministic rules-engine lookup for today's rhythm (干支/势能/almanac). It clearly conveys the domain and output concept, but does not explicitly differentiate itself from siblings like personal_day, time_fold, or sky_window, leaving the agent to infer the boundary.

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?

Provides explicit trigger phrases in both Chinese and English (今天节奏怎么样 / what is today's rhythm) and an implied negative ('Do not invent pillars or fortune claims'). It gives clear when-to-call context but names no alternative tool or when-not-to-use condition.

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