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

Annotations only declare readOnlyHint=false and destructiveHint=false; the description adds genuinely new context — irreversibility ('There is no undo') and the setup prerequisite. No permission/auth details, but the write nature and irreversibility are covered.

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-loads the core action, then adds the critical caveats and endpoint detail in order of importance. The endpoint-path sentence is dense but earns its place by preventing calls to the wrong sub-paths.

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 write tool with no output schema and terse annotations, the description covers the key facts an agent needs: prerequisite, irreversibility, and target endpoint. It falls short only on parameter-level detail (units/meaning) for the low-coverage 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 coverage is only 25% and three params are required, so the description must compensate. It loosely maps 'period and cycle lengths' to periodLength/cycleLength but adds no units, ranges, or meaning for options.predictedCycle. Marginal compensation for a low-coverage schema.

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 (confirms) and resource (menstrual period start) with the payload it carries (period and cycle lengths). It is clearly distinguishable from siblings like init_menstrual_cycle_setup, update_menstrual_calendar, and get_menstrual_last_confirmed.

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 an explicit prerequisite (cycle tracking must be set up in Garmin Connect first) and a strong caution (no undo). It doesn't name specific alternative tools to call instead, but the endpoint sentence routes the agent away from the wrong sub-paths.

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