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

The annotations already establish that the operation is read-only, idempotent, non-destructive, and closed-world. The description adds useful behavioral detail by listing the returned content: lunar date, can chi, hoàng đạo/hắc đạo classification, trực, lunar mansion, clashing ages, taboo days, and auspicious hours.

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 a single front-loaded sentence that states the action, scope, default, and result contents without unnecessary wording. Every listed result type is relevant to what the tool returns.

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 simple read-only lookup with one fully documented optional parameter and no output schema, the description is complete enough. It explains the input scope, default behavior, and enumerates the returned calendar fields an agent would need to understand the result.

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%, and the schema already explains that the date parameter is a Gregorian date in YYYY-MM-DD format and defaults to today in Vietnam. The description echoes the default behavior but adds no further parameter semantics beyond the schema.

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: it returns the Vietnamese lunar calendar entry for one Gregorian date. It clearly scopes the tool to a single date and enumerates the core result fields, though it does not explicitly distinguish itself from the close sibling convert_lunar_solar.

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?

Usage is implied by 'for one Gregorian date (default today),' which tells the agent this is a single-date lunar lookup. However, there is no explicit when-to-use or when-not-to-use guidance relative to convert_lunar_solar or find_good_days.

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