Cycle predict next period

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

Annotations already declare readOnly/idempotent/non-destructive behavior, and the description adds meaningful behavioral context: return values, acceptance of 21-90 day cycles in irregular mode, confidence capped at 'low', and a clinician-defer warning. This goes beyond the structured metadata.

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 sentences with zero waste: the first front-loads the core purpose, and the second adds a concise version-specific behavioral nuance. Every clause contributes meaning and the description is appropriately compact.

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 prediction tool with no output schema, the description covers the main return values and key behavioral constraints. However, it does not specify confidence value ranges, error/edge-case behavior (e.g., insufficient history), or what the clinician-defer warning entails, leaving some ambiguity for an agent.

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 67%, and the description adds extra semantics for cycle_irregular beyond the schema (accepts cycles 21-90 days, caps confidence at 'low', surfaces clinician-defer warning). history is less illuminated, but the schema already specifies the required structure and date pattern.

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 clearly states the verb ('returns'), the resource (period history), and the specific outputs (average cycle length, next-expected period start date, confidence). It also distinguishes itself from likely siblings like cycle_estimate_phase and cycle_irregular_check by focusing on next-period prediction rather than phase estimation or irregularity screening.

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?

The description gives clear context: use this tool when you have period history and need a predicted start date and cycle length. It also provides situational guidance for cycle_irregular mode tied to PCOS/unpredictable patterns. However, it does not explicitly mention alternatives or when not to use the tool.

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