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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior. The description adds material context beyond them: the data may be absent ('when available'), Garmin estimates must be kept distinct from logged records, and every response must be checked for serviceAnnouncements and those messages surfaced distinctly. That is genuine operational guidance, though it does not describe the shape of the summary itself.

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?

Three sentences, purpose front-loaded, each carrying distinct information (scope, interpretation rule, response-handling rule). The serviceAnnouncements sentence is longer than needed but earns its place by naming the exact field to inspect.

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 does well to name the serviceAnnouncements field and to flag the estimate-vs-logged distinction an agent would otherwise get wrong. It still leaves the actual contents of the cycle summary undefined, which is a modest gap for a single-parameter read tool.

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 single parameter (calendarDate, YYYY-MM-DD) is fully documented in the schema, including a format pattern. The description adds only 'for a date', which duplicates rather than extends the schema, so the 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?

States a specific verb and resource: reads the connected account's Garmin menstrual cycle summary for a given date. The 'summary' scope implicitly distinguishes it from garmin_get_menstrual_cycle_day, but no sibling is named explicitly, so an agent must infer the boundary from the name 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?

'when available' and 'Keep Garmin estimates separate from logged records' give interpretive guidance on using the result. There is no explicit when-to-use-vs-alternative statement pointing at garmin_get_menstrual_cycle_day or the wellness summary siblings, so routing is only implied.

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