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

readOnlyHint=true already tells the agent this is a safe read, so the bar is lower, and the description still adds real context: the required OAuth scope (read:cycles), the underlying REST endpoint, cursor-based pagination via nextToken, and the shape of each returned score (day strain, kilojoules, HR averages). It does not mention rate limits or error behavior, but it clears the annotation-adjusted bar.

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?

Four tight sentences with the core purpose front-loaded and no filler; the definition of 'cycle' comes before the mechanical details. The 'WHOOP REST: GET /v2/cycle' clause and the pagination parenthetical are mildly redundant with the schema, keeping it just short of a 5.

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?

There is no output schema, so the description correctly carries the return-value burden by naming the score fields (day strain, kilojoules, avg/max HR), and it also covers pagination, filtering, ordering, and required scope. An agent has everything needed to call this tool correctly without opening other tools.

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 four parameters are already documented in the schema. The description echoes the pagination (limit/nextToken) and created-time window (start/end) semantics without adding format or edge-case detail beyond what the schema states, so the baseline of 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 (List) and resource (physiological cycles), and goes further by defining the domain term as a WHOOP 'day' (~24h anchored to sleep), which an agent cannot infer from the name. Ordering ('most recent first') is also stated, so an agent can distinguish it from the singular whoop_get_cycle and the parallel list tools.

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 implies when to use it (bulk listing, filtered by created-time window) but never explicitly contrasts with siblings like whoop_get_cycle for a single cycle or whoop_list_recoveries for recovery data. Usage is inferable from the verb and filters, but there are no stated exclusions or alternative-routing guidance.

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