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

Annotations already declare a safe read (readOnlyHint, idempotentHint, non-destructive), so the bar is lower. The description still adds real behavioral context: the value is derived from solar-term boundaries rather than calendar months, and it discloses the endpoint and a 10-credit cost. It does not disclose how time/timezone affect boundary resolution.

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 core behavior, then a compact bracketed metadata block covering group, endpoint, requirement, and cost. Every line carries a distinct fact; nothing is padded.

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 no explanation, and the cost/endpoint metadata is present. For a solar-term-boundary calculation, though, the description never explains that the result depends on exact local time and timezone, nor does it distinguish itself from astroway_bazi_monthly — a meaningful gap for correct invocation.

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%, mid-range, and the description only repeats the required flag for 'date' — information already in the schema's required array. It adds no syntax, format, or defaulting guidance for time, language, or the boundary-critical timezone parameters, so it does not compensate for the coverage gap.

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 resource ('Month stem + branch') and a distinguishing mechanism ('from solar-term boundaries'), which sets it apart from astroway_bazi_year_pillar and astroway_bazi_hour_pillar by name. It does not, however, clarify its relationship to the confusingly similar sibling astroway_bazi_monthly or to astroway_bazi_four_pillars.

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?

Usage is implied by the name and by '[Required: date]' and the credit cost line, so an agent knows the minimum to invoke it. There is no explicit when-to-use vs. when-not guidance, and no routing between this tool, astroway_bazi_monthly, astroway_bazi_chart, and astroway_bazi_four_pillars, which overlap heavily here.

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