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

Annotations already declare the full safety profile (readOnly, idempotent, non-destructive, closed-world), so the burden is light. The description adds nothing beyond a field list that duplicates the existing output schema, and omits behavioral caveats that matter here — e.g. that the estimate assumes a regular cycle and ignores cycle variability.

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?

Two short sentences, front-loaded with the core purpose, no filler prose. Minor waste: the 'Returns: {next_period, ...}' enumeration restates keys already present in the output schema.

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?

Since an output schema exists, the return list is redundant rather than compensating. What is missing is the content only a description can carry: how this differs from calculate_ovulation, and the assumption set (regular cycles, 28-day default) behind the predictions.

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%: both cycle_length (default 28, range 21-45) and last_period_date (YYYY-MM-DD) are fully documented in the schema. The description adds no interpretation of these inputs, 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 (calculate) plus the exact resources produced: next period, fertile window, ovulation date. That is clear enough to identify the tool, but it offers no differentiation from the overlapping sibling calculate_ovulation (and calculate_pregnancy_due_date / calculate_due_date), which an agent in this 400-tool family would need.

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?

There is no when-to-use or when-not-to-use guidance. The only routing hint is 'See list_bundles for related "sante" calculators', which points at a catalog browser rather than telling the agent how to choose between this tool and calculate_ovulation.

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