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

Annotations already declare readOnlyHint=true and destructiveHint=false, so an agent knows this is safe and non-destructive. Beyond annotations, the description discloses that the response will include the source crystal alongside companion stones and their properties, giving a useful mental model of the returned data.

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 purposeful sentences with no filler: first defines the lookup action, second clarifies the return shape, and the final clause adds concrete use cases. It is immediately scannable and front-loaded.

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 presence of a complete input schema and a read-only annotation profile, the description adds the return-value context that the schema does not. The tool is small and well-scoped, so nothing essential appears to be missing for correct selection and invocation.

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 schema description coverage is 100%, so the schema already fully explains id, lang, and compact. The description's phrase 'given crystal' maps naturally to the id parameter, but it adds no meaning beyond what the schema already provides. 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 opens with a direct action, 'Get crystals that pair well with a given crystal,' clearly identifying both the resource and the operation. It further distinguishes this tool from general crystal-list siblings by specifying that it returns a source crystal plus companion stones. This is a specific, unambiguous resource method.

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 task-level use context—crystal grid building, healing combination recommendations, and cross-sell features—which helps an agent know when to use this pairing lookup. It does not explicitly contrast against siblings like get_crystals_random or get_crystals_search, but the use cases provide enough practical guidance.

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