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

Annotations already cover read-only and idempotent behavior. The description adds meaningful context: results are in Korea time, solar-term start times appear only on days when a term falls, and no birth data is needed. This goes beyond the annotations without contradicting them.

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 three sentences: the first lists the calendar contents, the second clarifies no birth data is needed, and the third gives usage examples. No sentence is wasted, and the main purpose is front-loaded.

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?

With an output schema present and annotations covering safety, the description is sufficient for an agent to decide when to call and what inputs to provide. It explains the scope (month/day), timezone, and the nature of the data, leaving only input format details to 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 100%, so the baseline is 3. The description's mention of 'month or a single day' and its example queries map to the date and month parameters, but it adds no semantic detail beyond what the schema already states (e.g., date overrides month).

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 names a specific resource (manse-ryeok calendar) and the exact data it returns: day/month/year pillars, lunar date, solar terms with Korea-time start times, and two flag types. It also gives concrete example queries that distinguish it from sibling tools like saju_chart, which require birth data.

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?

The description provides explicit example use cases ('what is today's day pillar', '이번 달 손없는날', '2027년 2월 일진'), making it clear when an agent should call this tool. It does not name sibling tools or state when not to use it, but the examples are strong enough to guide selection.

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