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

Annotations already cover read-only, idempotent, open-world, and non-destructive behavior, while the description adds the returned fields and the special case where period_may_be_late=true returns empty days and a doctor-suggestion line. However, that edge case references `days` and `period_may_be_late` without an output schema, and `days` is also an integer input parameter, creating minor ambiguity.

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?

It front-loads purpose and usage, then returns, exclusions, and edge case, making it easy to scan. The negative scope is repeated in several near-synonymous clauses, which is a small structural inefficiency but appropriate for a safety disclaimer.

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 nine-parameter, no-output-schema tool, the description gives enough to select and call it: purpose, usage, return fields, exclusions, and an edge case. It leaves the output structure and the origin/type of period_may_be_late and the 'say line' undefined, which keeps it from being fully complete.

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 nine parameters, including defaults, bounds, and aliases. The description adds little parameter meaning; its only parameter-adjacent note (days empty when period_may_be_late) does not map cleanly to the integer `days` input, so it cannot be credited as useful semantics.

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 the resource (the week ahead by phase) and the concrete return payload (each day's likely phase, workout focus, intensity, food focus), so it is not a tautology. It scopes itself to week planning, which helps distinguish it from the today-oriented sibling, though it does not explicitly name alternatives like get_todays_phase or list_phases.

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 an explicit trigger ('For when the user wants to plan training or meals for the week') with a user-phrase example, and it provides extensive negative scope ('Not for getting pregnant, fertile days, ovulation timing, contraception or pregnancy'). It also flags the period_may_be_late edge case, so the agent knows when the tool is and is not appropriate.

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