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

With no annotations, the description carries the burden and does well: it discloses the non-obvious computation rule (solar-term boundaries, year changing at Li Chun via an astronomical calendar engine) and enumerates what the result contains. It doesn't state that the operation is purely computational/non-mutating or discuss determinism or cost, but the methodology disclosure is genuinely useful.

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?

Three dense sentences: what it computes, how the calendar logic works, and what comes back. Nothing is repeated and the core purpose is front-loaded.

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?

With no output schema, the description compensates by enumerating return contents (four pillars, Ten Gods, Day Master, five-element balance, luck pillars, coming years), which is enough for an agent to know what it will get. The main remaining gap is guidance on choosing this over the sibling divination tools.

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 coverage is 100%, so the schema already documents all five parameters including the gender and language enums. The description adds only a high-level mention of birth date, optional birth time and timezone, and says nothing about gender or language, so it does not meaningfully exceed the schema baseline.

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 verb (Calculate) and a specific resource (BaZi / Four Pillars of Destiny chart), plus the exact inputs it derives from. It is clearly distinguishable from siblings like cast_i_ching, chinese_zodiac and draw_tarot_cards without opening any schema.

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 description implies when the tool applies (birth-data-based BaZi charting) and notes the birth time is optional, but it never states when to prefer it over chinese_zodiac or cast_i_ching, nor any exclusions or prerequisites. Usage is inferable rather than guided.

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