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

Annotations already cover readOnly/idempotent/non-destructive/closed-world, so safety is handled structurally. The description adds genuinely new behavioral context: this tool is scoped to general wellbeing and must not be used for medical or reproductive-planning questions, which the annotations cannot express. It does not say anything about output shape, but that is a minor 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?

Front-loaded and short overall, but the exclusion list is stated twice ('Not for conception, fertile days, contraception or pregnancy' then again 'not for pregnancy planning or contraception'), which is pure redundancy. The opening sentence also duplicates the title instead of adding information.

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 reference tool with no output schema, the description supplies everything an agent needs: what content comes back, when to invoke it, and the boundary conditions. Nothing material is missing.

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 has nothing to document and there is no coverage gap to compensate for. The description correctly frames the tool as date-free, which is the only 'parameter-like' constraint that matters here.

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 resource (cycle phase reference content: feelings, workouts, food ideas) and implicitly scopes itself against the date-based siblings via 'questions that need no dates'. The first sentence merely restates the title verbatim, which costs it a point, but the added scope sentence makes the tool distinguishable from get_todays_phase and get_week_ahead.

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?

Explicit when-to-use with a concrete example ('what should I eat in my luteal phase?') and an explicit when-not-use list (conception, fertile days, contraception, pregnancy). Routes the agent away from a whole class of intents without ambiguity.

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