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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered structurally. The description adds genuinely new context: the cost is plan-dependent and absent from the public credit manifest, and the input is case-insensitive. However it says nothing about response shape or rate limits, which is acceptable given the annotations and output 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?

Front-loads the actual purpose in one sentence, followed by compact bracketed metadata (group, endpoint, required param, cost). No wasted prose, though the bracket block is boilerplate that repeats schema-derivable facts like the required parameter.

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 annotations, an output schema, and full schema coverage, the basics are covered. The main gap is the absence of any routing guidance among the four sibling crystals tools, which is the primary decision an agent faces here.

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 the baseline is 3. The description's 'case-insensitive English name' note adds mild clarification, though it slightly diverges from the schema's 'lowercase English name' wording; it does nothing for the fields/precision compact-mode parameters, which the schema already documents.

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 the index dimension (zodiac sign), so an agent can distinguish it from the sibling 'by chakra' and 'by purpose' variants. It does not explicitly name those alternatives, but the purpose itself is unambiguous and specific.

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 gives no when-to-use guidance and never names the closely related crystals endpoints (astroway_esoteric_crystals, _by_chakra, _by_purpose, _recommend) that an agent must choose between. Only the mechanical [Required: sign] line is present, which is not usage guidance.

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