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

Annotations already declare the tool as read-only, idempotent, and non-destructive, so the safety profile is covered. The description adds a concrete return value ('Returns: {full_sign}'), which is useful behavioral context beyond annotations.

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 and front-loaded with the core purpose. The second sentence about list_bundles is a minor tangent but still relevant for discovery, and there is no excessive verbosity.

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 the tool's simplicity (one parameter, output schema present, annotations covering safety), the description is complete enough. It communicates what the tool does and what it returns; no critical gaps remain for an agent to invoke it correctly.

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 there is only one parameter, so the schema fully documents 'birth_year' including its range. The description adds no additional meaning beyond confirming 'from birth year', which is already in 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 states a specific verb ('Determine') and resource ('Chinese zodiac animal and element'), and clarifies the input ('from birth year'). It even specifies the return value ('Returns: {full_sign}'), making it fully distinguishable from other calculate_* tools.

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 implies usage (e.g., when you need a Chinese zodiac sign from a birth year) but provides no explicit guidance on when to use this tool versus alternatives. The pointer to 'list_bundles' for related calculators is a discovery aid, not a usage guideline for this specific tool.

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