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

Annotations already declare readOnlyHint=true, but the description adds real value on top: the required OAuth scope (read:cycles), the underlying REST endpoint (GET /v2/cycle/{cycleId}), and the payload contents (strain, kilojoules, avg/max heart rate, start/end). It does not discuss error behavior for invalid ids, but the added behavioral context exceeds the annotation baseline.

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?

Two compact clauses: the core action and returned fields first, then the REST route and scope. Every element is informative and front-loaded, with no filler or repetition of the title.

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 compensates by naming the returned fields, and it covers the auth scope needed to call it. Complete enough for a simple one-parameter read; only pagination/error semantics are absent, which are marginal here.

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 there is a single parameter, so the schema already documents cycleId fully (including the example provenance). The description adds no syntax or format detail beyond 'by its id', so 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?

States a specific verb (get), resource (physiological cycle), and scope (single, by id), and enumerates the returned fields. The phrase 'a single ... by its id' clearly distinguishes it from the sibling whoop_list_cycles, 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?

Usage is only implied: 'by its id' signals it needs an existing cycle id, and the schema note points to whoop_list_cycles as the source. There is no explicit statement of when to prefer this over whoop_list_cycles or any prerequisites/exclusions, so it sits at the minimum-viable tier.

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