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

Annotations already establish this as a safe, idempotent, non-open-world read. The description adds valuable behavioral context by specifying the returned data (signs, date ranges, latest forecast date), which is critical since no output schema exists; it does not repeat annotation details.

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, front-loaded sentence with no wasted words. The verb and scope appear immediately, and the sentence earns its place by clarifying the returned content.

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, parameterless list tool with rich annotations and no output schema, the description adequately conveys what will be returned. It does not explain ordering or pagination, but those are negligible for a fixed twelve-item list.

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?

The tool takes zero parameters, so the schema provides no parameter semantics. The baseline score of 4 applies for a parameterless tool; the description appropriately adds no parameter information.

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 provides a specific verb ('List') and resource ('the twelve zodiac signs') and enumerates what is returned (date ranges and latest forecast date). It implicitly distinguishes itself from find_sign and get_horoscope by scoping to the complete set of twelve signs, though it never names those siblings 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?

The description offers no when-to-use guidance, no prerequisites, and does not mention alternatives like find_sign or get_horoscope. It simply states what the tool returns, leaving the agent to infer appropriate usage.

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