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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds real context beyond that: the required auth scope (read:sleep), the endpoint, and the shape of what comes back (stage summary, sleep needed, respiratory rate, sleep performance %, start/end). It does not discuss errors for invalid/expired ids, which keeps it short of a 5.

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?

A single dense sentence that front-loads the action and id requirement, then packs endpoint, returned fields, and scope with no filler. Every clause carries information an agent would otherwise have to infer.

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?

For a one-parameter read tool with no output schema, the description supplies the return fields, the auth scope, and the endpoint, while annotations cover the safety profile. Nothing needed to invoke it correctly is missing.

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 the schema already explains that sleepId is a UUID obtainable from whoop_list_sleep. The description adds nothing about the parameter beyond what the schema states, so the baseline 3 applies.

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 verb and resource ('Get a single sleep activity by its id') and pins it to the exact WHOOP REST endpoint GET /v2/activity/sleep/{sleepId}. The word 'single' cleanly distinguishes it from the sibling whoop_list_sleep, so an agent can route without opening either schema.

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?

'By its id' establishes the retrieval precondition and implies use only after a sleep id is known, and the schema explicitly points to whoop_list_sleep as the id source. There is no explicit when-not guidance, but for a by-id fetch the usage context is unambiguous.

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