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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds one genuinely useful behavioral fact beyond that: the call costs 1 credit. It does not mention that predictions are estimates with inherent variability, which would matter for a health-adjacent prediction tool.

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?

The sentence structure is front-loaded and the credit cost is a useful trailing note. However, the name is repeated verbatim immediately after the colon ('Menstrual Cycle Calculator: Menstrual Cycle Calculator is...'), which is pure waste in an otherwise short description.

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 an output schema present and annotations covering the safety profile, the description only needs to convey what the tool computes and its cost, and it does both. The main gap is the absence of any sibling disambiguation against OvulationCalculator, which is a meaningful ambiguity for an agent choosing between period-tracking tools.

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 the schema already documents all four parameters including defaults and the YYYY-MM-DD format for last_period. The description restates three of the inputs but never mentions the 'cycles' parameter controlling how many future cycles to compute, so it adds nothing beyond the 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?

The description states a specific verb and resource set: it predicts future menstrual cycles, fertile windows, and ovulation dates from last period date plus average cycle and period lengths. That is far more informative than the name alone. It does not distinguish itself from the sibling OvulationCalculator, which covers overlapping territory, so it misses a 5.

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 through the listed inputs, so an agent can infer the tool is for forward-looking cycle prediction from a known last period date. There is no explicit when-to-use or when-not-to-use guidance, and no mention of the OvulationCalculator sibling or which one to prefer for ovulation-only questions.

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