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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds real value by disclosing what the result contains (Ten Gods, Hidden Stems, Na Yin, Shen Sha, Five-Element strength), which matters because there is no output schema. It does not mention the default solar_time or any date-range/validation behavior, keeping it short of a 5.

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?

A single front-loaded sentence that names the operation first and then lists outputs; no filler or repetition. The dense enumeration is justified because it substitutes for a missing output schema.

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 read-only chart generator with fully documented parameters and no output schema, the description covers both what it does and what it returns. Minor gaps remain around timezone/lunar-conversion assumptions and how gender affects the chart, but nothing essential to invoking it correctly 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 all three parameters (gender, solar_date, solar_time) are already documented in the schema, including the 08:30 default. The description adds no additional meaning about formats, accepted gender values, or timezone handling, so the baseline 3 applies.

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 ('Lập' = cast/create) plus a specific resource ('lá số Bát Tự Tứ Trụ') and enumerates the chart components produced (Can Chi 4 trụ, Thập Thần, Tàng Can, Nạp Âm, Thần Sát, Ngũ Hành statistics). This clearly separates it from siblings like tuvi_chart_vn or calculate_numerology by domain, though it never names an alternative explicitly.

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 when-to-use guidance, no prerequisites, and no mention of when a different chart tool (tuvi_chart_vn, get_birth_chart, calculate_numerology) would be the better choice. The agent must infer the use case entirely from the tool name and the enumerated outputs.

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