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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description usefully adds that Samjae and the year relation are rule-derived (deterministic) while the narrative reading is Korean text, but it leaves an unresolved tension with the lang parameter's 'en' option and says nothing about response size or structure.

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?

A single dense sentence that front-loads the year and resource, then lists the returned components; there is little waste. It is long but each clause carries content, though the parenthetical transliterations (丁未 Jeongmi, 삼재) are somewhat decorative.

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 no output schema, the description compensates by enumerating the returned sections (overall luck, money, love, health, work, monthly, lucky points), which is the key missing structured information. The only real gap is the unexplained interaction between the lang parameter and the stated Korean-only reading text.

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%, with the animal parameter already documenting Korean/English names and birth-year input, so the schema does the heavy lifting. The description restates the birth-year acceptance and adds that output text is Korean, but does not clarify how lang=en interacts with that claim.

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: the 2027 New Year fortune for a zodiac animal, and enumerates what the answer contains (Samjae, relation to the 未 year, birth years, reading sections, lucky points). The '2027 New Year' scope implicitly separates it from get_daily_zodiac_fortune, but no sibling is named explicitly.

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 only implied: an agent can infer this is the annual 2027 reading rather than a daily one, and that a zodiac animal or birth year is accepted. There is no explicit when-to-use/when-not statement or pointer to calculate_saju or get_daily_zodiac_fortune as alternatives.

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