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

Annotations already declare readOnlyHint=true and destructiveHint=false, covering the safety profile. The description adds valuable behavioral context beyond that: it specifies cycle ordering from Rat to Pig, lists exactly what each entry contains, and notes the intended use case. It does not mention pagination behavior or language fallback, but those are documented in the parameter schema.

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 two sentences long with no filler. The first sentence states the action and ordering; the second enumerates return fields, which is necessary since there is no output schema. The final phrase about the intended use earns its place by clarifying scope. The structure is front-loaded and tightly packed.

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 there is no output schema, the description compensates by listing the return fields. It covers the core behavior, ordering, and use case. It does not explicitly describe pagination or the effect of offset/limit on the 'whole set' promise, but those details are in the param schema. A mention of the single-id sibling would improve completeness, but the tool name provides a hint.

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 each of the four parameters (lang, limit, offset, compact) already has a clear description. The tool description adds no parameter-specific meaning, which is acceptable because the baseline of 3 applies when the schema carries the full burden. No compensation needed.

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 starts with a specific verb and resource: 'Retrieve all twelve Chinese zodiac animals in cycle order, from Rat through Pig.' It enumerates the exact fields returned (machine id, Chinese character, pinyin, Earthly Branch, Five Element, yin/yang, traits), which uniquely positions it against siblings like get_chinese_astrology_zodiac_animals_id. The title reinforces the 12-animal catalogue, making the tool's purpose unmistakable.

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 clearly states the intended scenario: 'Built for sign pickers, zodiac cards and compatibility widgets that need the whole set in one call.' This gives context for when to choose it over a single-animal lookup. It does not explicitly name an alternative tool or state when-not-to-use, but the 'whole set in one call' phrasing provides a functional boundary.

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