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

Annotations already cover read-only, idempotent, non-destructive, closed-world safety. The description adds genuine value beyond them by disclosing the year-boundary rule (the year turns at Li Chun, computed from the exact solar term), which affects how a given input date is interpreted. It does not describe pagination, return shape, or the interaction of date/year/time inputs.

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 dense, front-loaded sentences that enumerate the outputs first and the optional layer and year boundary after. No padding, though jargon density means a non-domain reader gains little.

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?

Percentages: an output schema exists so return values need not be explained, and annotations carry the safety profile. But for a 9-parameter tool with 44% coverage and a near-duplicate sibling, the definition leaves the input contract and tool-selection decision underspecified.

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?

Nine parameters at 44% schema coverage, so the description must carry more weight than it does. It maps 'Optionally the monthly layer' to includeMonthly, but says nothing about how date, year, time, timezone, or fields interact or which should be supplied. The parameter surface is left largely unexplained.

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?

Specific verb+resource: the nine annual stars for a solar year plus named afflictions (Tai Sui, Sui Po, San Sha, five yellow, two black) with sectors, and an optional monthly layer. Clear what is produced, but it never distinguishes itself from the near-identical sibling astroway_chinese_feng_shui_flying_star, so an agent cannot route between them from the text alone.

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?

Only implicit guidance: 'Optionally the monthly layer' hints at when to add the monthly data. There is no statement of when this tool is preferred over astroway_chinese_feng_shui_flying_star or the other feng-shui siblings, and no prerequisites or exclusions are given.

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