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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered by structured data. The description contributes the cost tier (10 credits, Tier 1) and the endpoint, which are useful operational facts not present in the annotations, but says nothing about whether the result is deterministic across timezone settings or how time/timezone affect the pillar.

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 output summary is front-loaded in one line and the bracketed metadata block is compact and scannable. Nothing is padded, though the boilerplate labels (Group/Endpoint/Required/Cost) consume most of the description's real estate relative to actual explanation.

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-value detail is fairly excused, but the central ambiguity remains unresolved: whether `date` is the subject's birth date or the calendar year being inspected, and how `time`/`timezone` interact with that. For a 7-parameter tool with partial schema coverage and several confusable siblings, the definition leaves too much to inference.

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 57%, and the three undocumented parameters are the semantically critical ones: date (no description at all — birth date vs. target year is ambiguous), time, and language. The only param-related text, 'Required: date', merely restates the schema's required array and adds no meaning.

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 first line names a specific output bundle — year stem, branch, animal, element, yin/yang — for the BaZi year pillar, which is a concrete verb+resource an agent can recognize. It does not, however, contrast itself with near-identical siblings like astroway_bazi_month_pillar, astroway_bazi_hour_pillar, or astroway_bazi_year_pillar_decade, so the agent must infer the distinction from the name 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?

The definition never says when to pick this tool over astroway_bazi_four_pillars or astroway_bazi_chart, nor what question it answers. The only routing-style hints are boilerplate ('Required: date', 'Cost: 10 credits'), which tell the agent nothing about appropriate usage.

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