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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new behavioral context: results may be absent ('when available'), Garmin-derived estimates must be presented separately from user-logged records, and every response must be checked for serviceAnnouncements from the independent operator and surfaced distinctly.

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?

Purpose is front-loaded in the first sentence, followed by parameter guidance and then the response-handling obligation. Three sentences carry no filler, though the serviceAnnouncements instruction is a policy directive rather than a tool-selection aid and slightly dilutes the operational focus.

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, five-parameter tool with no output schema, the description supplies purpose, date semantics, analysis opt-in, availability caveats and response-handling duties. It stops short of describing what the returned cycle details contain (e.g., cycle day, phase, predictions), which is the main remaining gap given the absence of an output schema.

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 five parameters (including skipbm and reducedResponse) are already documented in the schema, establishing a baseline of 3. The description reinforces intent for todayDate and includeAnalysis but adds little syntax or meaning beyond what the schema states, and it is silent on skipbm and reducedResponse.

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 ('Read') and a narrowly scoped resource ('Garmin menstrual cycle details for one date'), plus the availability caveat 'when available'. It does not explicitly contrast with the sibling garmin_get_menstrual_cycle_summary, so an agent must infer the single-date vs. summary split from the resource phrasing alone.

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?

Gives conditional guidance for two parameters ('use todayDate for the current date in the user's time zone', 'includeAnalysis when Garmin's own analysis is requested') and a data-handling rule about keeping estimates separate from logged records. However, it never names the summary sibling or states when not to use this tool, so the routing decision is left implicit.

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