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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered. The description adds genuinely new behavioral context: the output is a score out of 100 with each contributing factor explained, which tells the agent what to expect back despite the absence of an output schema.

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 well-formed sentence that front-loads the operation and ends with the return contract; no filler or repetition of the title.

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 nested two-object tool with no output schema, the description covers the computation basis and return shape adequately. Minor gaps remain around the optional name field and input bounds, but an agent can call this correctly from what is given plus the schema.

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 effectively 0% beyond the gender enum note, so the description must compensate. It does convey that birth_year and gender are the inputs that drive the calculation, but it never mentions the optional 'name' field, the 1920–2100 year bounds, or how gender affects the Bát Trạch cung phi computation.

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 and resource ('Compares two people by birth year and gender') and enumerates the exact frameworks used (nạp âm, heavenly stem, earthly branch, Bát Trạch cung phi, zodiac animal). It implicitly separates itself from the sibling find_compatible_birth_years by comparing two concrete people rather than returning year lists, though it never names that sibling to make the distinction explicit.

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?

Nothing states when to pick this over find_compatible_birth_years or create_tuvi_chart; the two-person comparison framing implies match-making/pairing use cases but the agent must infer it. There are no exclusions or prerequisites called out.

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