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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds no behavioral context of its own: nothing about error handling for an unknown gym id, whether the join/booking links imply authentication, or any caching/rate-limit behavior.

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?

One compact sentence with the resource front-loaded and the returned fields listed without filler. It is a noun phrase rather than a sentence, but every element earns its place and nothing is redundant.

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 no output schema, the description correctly compensates by enumerating the returned detail fields, and the annotations cover the read-only safety profile. Missing only edge-case behavior (unknown/mismatched gym id, locale fallback semantics) for full completeness.

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% and both parameters (gym identifier, locale enum with default fr) are fully documented in the schema. The description adds no syntax or format detail beyond that, so the baseline 3 is the right level.

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 ('a Gymmy gym') and enumerates the content returned (description, address, opening hours, sites, booking info, links), so the agent knows exactly what it fetches. It does not, however, contrast itself with siblings like search_gyms or my_gyms, so the differentiation is left 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?

The description contains no when-to-use, when-not-to-use, or alternative-tool guidance. The only routing hint — that the `gym` id comes from search_gyms — lives in the input schema, not the description, so the description itself gives the agent nothing to select on.

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