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

Annotations already cover safety (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false). The description adds genuinely non-annotation context: the output is date-independent and the call costs 5 credits (Tier ½), plus the endpoint. It does not describe return shape or auth, but the added cost/determinism context is real value.

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?

Two front-loaded sentences carry the substance, followed by a compact metadata block. No padding or repetition; the ordering is sensible.

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 and rich annotations exist, so the description need not explain returns, and it adequately covers the reference-table purpose. The unresolved tension between 'required: date' and 'does not vary with the date' is the one gap an agent would want clarified.

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 67% and the description adds no syntax or meaning for 'date', 'time', 'fields', 'timezone', 'precision', or 'timezoneOffset'. It actually creates a mild tension by declaring the table does not vary with the date while the schema marks 'date' as required, leaving the agent to guess why. Baseline 3 is appropriate given the schema does most of the work.

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 (the 14 main stars) and scope (canonical order, Zi Wei then Tian Fu series, with theme/archetype). The phrase 'Reference table: does not vary with the date' differentiates it from the many date-driven ziwei siblings such as ziwei_chart or ziwei_full_chart. It is clear but never names an explicit sibling.

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?

Implies usage by noting it is a static reference table, which suggests lookup rather than chart computation, but it never states when to pick this over astroway_ziwei_chart, astroway_ziwei_twelve_palaces, etc. No prerequisites or exclusions are given.

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