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

Annotations already declare this is a safe, closed-world read (readOnlyHint=true, destructiveHint=false, openWorldHint=false), so the safety profile is covered. The description adds genuinely useful domain behavior beyond that: true solar time from birthplace longitude, historical daylight-saving rules, the 23:00 Day Pillar rollover, and Lichun/solar-term boundaries. It still doesn't say whether results are cached or how the card is delivered, so it isn't exhaustive.

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?

Purpose, trigger conditions, computational rules and post-call behavior are front-loaded in that order with no filler. It is on the long side for a single tool, and the final interpretation sentence could be tightened, but every sentence carries operational meaning.

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?

For a domain-heavy calculation tool with no output schema, the description supplies what an agent needs: the inputs it draws on, the calendrical rules that determine the result, that the chart card is the user-facing artifact, and how to respond afterward. Nothing essential to correct invocation is missing.

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 100%, so the schema already explains gender, language, timezone, longitude, birth_date, birth_time and birthplace. The description reinforces why longitude and birthplace matter (solar-time correction vs. user's current location), but adds no syntax or edge-case detail beyond the schema. Baseline 3 applies when structured fields carry the parameter burden.

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 opens with a precise verb-plus-resource statement ('Calculates a BaZi ... chart from a birth date, time and place with the InsightBaZi engine') and includes the alternate names users may use (Four Pillars, 八字, Saju), so an agent can match many phrasings without ambiguity.

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 states explicitly when to use it ('when the user asks for a BaZi chart, or for their Four Pillars, Day Master, Ten Gods, element balance or 10-year luck pillars') and what to do after calling it: confirm briefly, don't duplicate the chart, interpret only if requested. That is both selection guidance and post-call routing.

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