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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the description's job is lighter. It adds valuable context by stating it applies True Solar Time correction and requires the subject's permission, which goes beyond the annotation-provided profile.

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?

The description is well-structured: first sentence states the primary use case, second sentence lists exclusions (plus a permission note). It is somewhat long due to bilingual repetition, but every clause contributes directly to correct invocation, making it appropriately concise.

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?

Given that an output schema exists and parameter descriptions cover the inputs, the description sufficiently covers usage conditions, required data, and behavioral notes. It lacks explicit mention of output format, but that is the output schema's responsibility. It is complete enough for an agent to call correctly.

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?

With 100% schema coverage, the baseline is 3. The description adds semantic nuance by referring to the 'historical UTC offset,' clarifying that the timezone parameter is for the birth date, not the current one. This is a meaningful addition beyond the schema's simple offset description.

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 states a specific verb-resource pairing: it calculates a Four Pillars birth chart given explicit birth data. It distinguishes itself by explicitly excluding inference of missing details or personalized guidance, which differentiates it from sibling tools like get_daily_bazi_guidance.

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?

It provides explicit when-to-use ('when the user wants a Four Pillars birth chart and has explicitly supplied...') and when-not-to-use ('Do not use this to infer missing birth details, daylight-saving rules, or personalized guidance') conditions, effectively routing the agent to the correct tool. The additional consent requirement adds a practical usage constraint.

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