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

Annotations already declare read-only and closed-world, and the description adds the meaningful behavioral fact that results are computed across a rolling 'next few days' horizon, which explains the idempotentHint=false. It also enumerates the returned fields (date, hour branch, true-solar-time range, score, lucky direction). It does not mention cost/latency of scanning up to 84 double-hours.

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?

Two sentences, both earning their place: the first covers computation and ranking, the second covers the return payload. Nothing is repeated from the title or schema.

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 return-value burden and does so adequately by listing the output fields. The remaining gap is operational (expected runtime for a multi-day scan) and edge-case behavior, which is minor for a read-only analytical tool.

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 goes beyond it by tying birth_date to the Day Master and longitude to the true-solar-time range, clarifying why those inputs matter. It still doesn't clarify how 'focus' changes ranking or how 'top' interacts with 'days'.

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 verb and resource ('Cast a Qi Men chart for every double-hour'), the scope ('next few days'), and the operation ('rank them for a goal'). It also names the data source (Day Master from the birth date), which makes it clearly distinct from a single-chart sibling like qimen_chart.

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 use case (find ranked windows for a goal) is implied by the description, but there is no explicit when-to-use / when-not-to-use guidance and no named alternative such as qimen_chart for a single-moment reading. The agent must infer the routing.

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