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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds meaningful domain boundaries in 'general wellbeing only, not for pregnancy planning or contraception', which goes beyond the structured fields. It does not describe the response shape, which is the remaining gap.

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?

Usage guidance and exclusions are front-loaded and each sentence earns its place. The first sentence restates the title verbatim, which is mild redundancy, but the rest is tight and well ordered.

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 zero-parameter, read-only, no-output-schema tool, the description covers scope, intended questions and exclusions adequately. The main omission is any hint of what the response contains structurally (e.g. all phases vs. a summary), which an agent might want before calling.

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?

The tool takes zero parameters, so the schema carries no burden the description must compensate for. Baseline 4 applies; there is nothing further for the description to clarify about inputs.

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 identifies the resource (cycle phases) and what it returns: what each phase feels like, plus workout and food ideas. It is clear enough to distinguish from date-dependent siblings by noting it needs 'no dates', though it never explicitly names those siblings or uses the verb 'list'.

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?

It gives explicit when-to-use ('general questions about cycle syncing that need no dates') with a concrete example ('what should I eat in my luteal phase?'), and explicit when-not-to-use ('Not for conception, fertile days, contraception or pregnancy'). Nothing is left to inference.

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