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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely useful behavioral context beyond that: it discloses the credit cost (10 credits, Tier 1) and the group, which an agent needs for planning. It stops short of describing format, pagination, or any rate/limit behaviour.

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?

One dense but well-structured sentence front-loads the core purpose and output list, followed by two short bracketed metadata lines (group, cost). There is no filler, though the single sentence is somewhat list-heavy.

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 description usefully signals what the payload contains. However, with 7 parameters at 57% coverage and no usage guidance versus the tong_shu_select sibling, the definition leaves an agent guessing about routing and about the un-documented date/time/language parameters.

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 description adds no parameter meaning whatsoever — nothing about date, time, language, or how 'fields'/'precision' compact mode interacts with this endpoint. The rich timezone/timezoneOffset descriptions live in the schema, not the description, so the description does nothing to close 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?

The description gives a specific verb+resource ('the almanac reading of one day') and enumerates the exact contents returned: day pillar, day officer (建除十二神) with endorsements/forbids, the 28 mansion with quadrant and planet, and the clash animal. That is far more concrete than the name alone. It does not, however, distinguish this single-day tool from the close sibling astroway_chinese_tong_shu_select, so the agent must infer the boundary.

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?

There is no explicit when-to-use or when-not-to-use statement. The phrase 'the almanac reading of one day' implies a single-date scope and hints at a range-selecting sibling, but no alternative is named and no prerequisite or selection condition is given.

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