Menstrual cycle (one day)

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

Goes beyond the read-only/idempotent annotations by disclosing the return structure (summary and dayView) and the important emptiness condition. It does not describe error behavior for dates without data, but the core behavioral picture is clear.

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?

Single dense paragraph that front-loads what is returned and then the date constraint. A clause duplicating the schema's date formats is mild waste but the rest earns its place.

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 the necessary work of explaining the two-part return (summary, dayView) and when it will be empty. For a single-parameter read tool this is sufficient to call correctly.

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 coverage is 100% and the schema already documents YYYY-MM-DD plus 'today'/'yesterday' with timezone resolution, so the description's restatement of the accepted formats adds no new meaning. The only added value is the one-call-per-date instruction.

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?

Names a specific resource (menstrual cycle) and scope (one date), and the title confirms the granularity. It is clearly distinct from every sibling, none of which touch cycle data, though it does not explicitly say so.

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?

States the key constraint 'call once per date', which tells the agent this is not a range query, and notes the data is empty unless the user tracks cycles in Garmin Connect. It does not point to any alternative for multi-day or historical ranges, so the exclusion side is only implied.

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