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

Annotations only give readOnlyHint=true, so the description carries the rest: it discloses ordering, the shape of each cycle's score payload, pagination mechanics, the created-time filter window, and the required read:cycles scope. It does not describe rate limits or error behavior, but adds substantial context beyond the annotation.

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?

Five tight sentences, each contributing distinct information: domain definition, payload contents, pagination, filtering, and endpoint/scope. Front-loaded with purpose and free of filler.

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 usefully names the returned fields (day strain, kilojoules, heart rate) and the next_token cursor. Combining the endpoint, scope, and filter semantics makes it callable without further guesswork; only response envelope details are left implicit.

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 coverage is 100%, so all four parameters are already documented in the schema. The description restates limit/nextToken pagination and the start/end window without adding format or defaulting detail beyond what the schema provides — baseline 3 is correct.

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 ('List the user's physiological cycles'), defines the domain term ('a WHOOP day, ~24h anchored to sleep'), and specifies ordering, contents, pagination, filters, and the underlying endpoint. This clearly separates it from the singular sibling whoop_get_cycle.

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?

Conveys implied usage through 'most recent first' and 'filterable by created-time window', but never states when to prefer this over whoop_get_cycle or how it relates to whoop_list_recoveries/whoop_list_sleep. The agent must infer list-vs-get from the name alone.

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