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

Annotations already declare readOnlyHint and openWorldHint=false, so safety is covered; the description adds beyond that by describing the returned payload (animal, stem element, yin-yang, start/end New Year dates). The 'needs no personal data' note is useful privacy context for an agent deciding whether to ask the user for input, though pagination/errors are irrelevant here.

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?

Two sentences, zero filler: the first defines the output, the second gives the motivating use case. Both are front-loaded and every clause carries information.

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 single-parameter read-only lookup with no output schema, the description is sufficient: it names the returned fields and the ambiguity the tool resolves (Lunar New Year boundaries). Nothing an agent needs in order to call it correctly is missing.

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 coverage is 100% and the schema already explains that the year is the one beginning at that calendar year's Lunar New Year, so the description duplicates rather than extends that. It does reinforce the edge-of-year semantics through the January/February example, but adds no bounds or format detail 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?

States a specific verb and resource ('Look up a Chinese zodiac year') and even enumerates the fields returned (animal, stem element, yin-yang, New Year dates). It only weakly distinguishes itself from the sibling calculate_birth_date_profile, via the implicit 'needs no personal data' contrast rather than naming it.

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?

Supplies a concrete use case: explaining why a January or February birthday falls under the previous animal, which tells the agent exactly when this tool is the right call. It also signals the alternative data path by noting no personal data is required, but gives no explicit exclusion or when-not-to-use statement.

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