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

Annotations already declare readOnlyHint=true and destructiveHint=false. The description adds context about it being entertainment-only and returning a summary, but doesn't detail auth needs or potential side effects. Adequate but not exceptional beyond what annotations provide.

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?

Five sentences, front-loaded with purpose, concise list of use cases, and caveat. No fluff, though could integrate the caveat more tightly. Good structure.

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 complexity (14 params, 6 required) and presence of output schema, the description covers what the tool returns (Day Master relation), input format (Gregorian), and cultural context. Minor gap: doesn't explicitly state the output format structure, but output schema fills that. Complete enough.

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 baseline is 3. The description provides high-level context (Gregorian birth data, optional hour/country) but doesn't add significant meaning beyond the schema's individual parameter descriptions. Overall satisfactory.

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 clearly states it computes two-person compatibility from Gregorian birth data, returning Day Master Five Element relation. It uses specific verbs ('compares charts and returns') and distinguishes from sibling tools (calculate_saju, get_day_master, list_stems_and_branches) by focusing on pairwise comparison.

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?

Explicitly lists use cases (soulmate, twin flame, partner, etc.) and conditions ('when two dates are available'). Adds caveat ('Entertainment / cultural signal only') and directs to external resource for depth, providing clear when-to-use and when-not-to-use guidance.

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