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

With readOnlyHint/openWorldHint already declaring the safety profile, the description still adds real value: the deterministic charting method, the Asia/Shanghai timebase, the absence of true-solar-time correction, and what the returned palace data contains. It does not discuss the supported year window or any failure behavior, keeping it below 5.

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?

Front-loaded with the action and method, then the timebase caveat, then the return payload. Dense but each clause carries information; the parenthetical Chinese name and method detail are somewhat heavy but not wasteful.

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 enumerates the returned fields (four pillars, Dun/Ju, Zhi Fu/Zhi Shi, nine palaces with stars, doors, deities, patterns, void/horse markers), so an agent knows what to expect. Only the undocumented year range and minute parameter keep it from being fully complete.

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 only 20% — just the hour param — so the description partly compensates by specifying that all date/time inputs are Beijing time (UTC+8). It says nothing about minute (defaults to 0) or the 1900–2200 year bounds, so gaps remain.

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 Qimen Dunjia hour chart) plus the exact method (Chaibu bureau, rotating plate) and reference timebase. It implicitly separates itself from qimen_chart_now by requiring an explicit date/time, but never names the sibling explicitly.

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?

Gives concrete input-preparation guidance: convert other local times to UTC+8 first, and no location or true-solar-time correction is applied. It lacks an explicit 'use qimen_chart_now instead when...' routing statement, so the alternative is left to inference from the sibling name.

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