Crystals by Zodiac Sign

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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds two genuinely extra facts: input is case-insensitive, and the endpoint has an unclear credit cost ('not in the public credit manifest'), which is useful for an agent budgeting calls. It says nothing about result shape, but an output schema exists.

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 core sentence is front-loaded and one line long, with zero padding. The bracketed metadata block (group, endpoint, required, cost) is template boilerplate but does carry the cost caveat, so it is not entirely wasted.

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?

A single-parameter lookup with full schema coverage, an output schema, and complete safety annotations needs little more. The only meaningful gap is the absent note on output content/volume and on what happens for an invalid sign, but the output schema covers much of that.

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 single `sign` parameter is documented, so baseline is 3. The description's 'case-insensitive' note adds meaning beyond the schema, but it slightly conflicts with the schema's 'lowercase English name', leaving the accepted format ambiguous rather than clarified.

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 resource (crystals) and a specific index (zodiac sign), which lets an agent distinguish it from the sibling crystal tools (by_chakra, by_purpose, recommend, plain list). It does not explicitly name those alternatives, but the sign-indexed scope is unambiguous.

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?

No explicit when-to-use or when-not guidance, and no reference to the sibling crystal endpoints that cover chakra/purpose/recommendation lookups. Usage is only implied by the required `sign` parameter, so the agent must infer routing from the tool name.

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