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

Annotations already declare readOnly, idempotent, non-destructive, non-open-world, so the safety profile is covered. The description adds genuine behavioral context beyond that: that seven stems are tradition-invariant, that three vary, that every variant ships in `schoolVariants`, and that `school` swaps the headline answer. This discloses output-shaping behavior an agent would otherwise not know.

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 core is two front-loaded sentences that define the tool before the caveats, with no wasted prose. The trailing metadata block (group/endpoint/required/cost) is boilerplate but compact and useful for the required param and cost.

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?

An output schema exists, so return values need not be spelled out. For a 7-param tool with one required field, the description supplies the conceptual model and the school-variant behavior. It is adequate, though it says nothing about the time/precision/tz params that could matter for date resolution.

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 57% across 7 params. The description gives real meaning to `school` (it switches the headline answer and co-exists with schoolVariants), which the bare enum does not. The other params (time, fields, precision, timezone, timezoneOffset) are left entirely to the schema. Baseline 3 fits.

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 (the four transformations 四化), defines each of the four stars (化禄/化权/化科/化忌), and carves out its niche versus the star-placement siblings by stating it is 'the one part of Zi Wei computable without star placement'. An agent can tell what it returns and how it differs from ziwei_main_stars or ziwei_full_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?

It explains the school-dependent behavior and that seven stems are agreed while three (戊 庚 壬) vary, which implies when `school` matters, but it never states when to call this versus an alternative tool or any prerequisite beyond the required `date`. Usage is inferable but not routed explicitly.

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