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

Annotations only declare readOnlyHint=true. The description adds real behavioral context beyond that: the underlying REST endpoint (GET /v2/cycle/{cycleId}) and the required OAuth scope (read:cycles), which tells the agent what auth is needed. It does not discuss error behavior for an invalid id, but that is minor.

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?

Front-loaded purpose followed by returned fields, endpoint, and scope in a compact block with no filler. The endpoint path is slightly redundant but is legitimately useful identifying context.

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 read-only single-resource fetch with no output schema, the returned-field list compensates well for the missing return documentation, and the scope note covers auth. Only explicit routing to whoop_list_cycles is absent.

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 states cycleId is an integer obtainable from whoop_list_cycles. The description adds no parameter semantics beyond that, so 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?

Specific verb+resource ('Get a single physiological cycle by its id') plus the payload fields it returns. The word 'single' differentiates it from whoop_list_cycles implicitly, though no sibling is named explicitly.

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 implied by 'by its id', which suggests the agent must already have a cycle id, but there is no explicit when-to-use vs when-not guidance and whoop_list_cycles is not named as the alternative for enumerating cycles.

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