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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description adds a genuinely useful non-schema detail — substring matching semantics (also mirrored in the schema) and a cost caveat that the endpoint is absent from the public credit manifest. It adds some value, but not rich behavioral detail beyond that.

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 opening sentence is front-loaded and waste-free, and the bracketed metadata block (group, endpoint, required param, cost note) is compact and scannable. Slight redundancy between the description's substring-matching mention and the schema's own note, but overall efficient.

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 a 100%-covered schema, rich annotations, and an output schema handling return values, the description only needs to orient the agent — which it does. The one real gap is sibling differentiation against the other crystal endpoints, which a competent agent can partially recover from the tool name.

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 all three parameters (purpose, fields, precision) are already documented, including the substring-match example. The description's phrase 'indexed by intent keyword' loosely maps to the purpose parameter but adds nothing the schema does not already say. Baseline 3 is appropriate.

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 resource and scope: crystals indexed by intent keyword, with concrete examples (love, prosperity, healing, protection). This is clear enough to distinguish it from a generic crystal listing, but it never differentiates itself from the closely-named siblings (by_chakra, by_zodiac_sign, recommend), leaving that routing to inference.

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?

Usage is implied by the examples and the 'match a purpose' framing, so an agent can infer this is the tool for intent-based crystal lookup. There is no explicit when-to-use or when-not guidance, and no mention of the by_chakra / by_zodiac alternatives that would be the natural confusion points.

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