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

Annotations already cover readOnly/idempotent/non-destructive, so the bar is lower. The description adds genuine behavioral context beyond that: the period_may_be_late edge case where days comes back empty and the say line recommends a doctor, plus the domain-scope caveat that this is not a fertility calendar.

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 with purpose and usage, which is good, but the opening restates the name/title and the disclaimer is repetitive, saying contraception/pregnancy twice ('not for ... contraception or pregnancy ... not for pregnancy planning or contraception'). Trimming the duplication would tighten it.

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?

With 9 parameters, no output schema, and complex cycle math, the description usefully previews the return fields and flags the empty-days edge case. It is close to complete, though it could note the 120-day last_period validity constraint that the schema carries.

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 every parameter (tz, date, days, diet, country, last_period, cycle_length, period_length, last_period_start) is already documented in the schema. The description adds no parameter-level meaning beyond that, 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 concrete verb+resource (week-ahead day-by-day phase plan) and enumerates the returned fields (phase, workout focus, intensity, food focus). This clearly differentiates it from the sibling syncmycycle_get_todays_phase, which covers a single day.

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?

Gives an explicit trigger ('Use when the user wants to plan training or meals for the week') with a sample utterance, plus firm when-not boundaries around fertility/pregnancy/contraception. It never names a sibling tool (e.g., get_todays_phase) as the alternative, so routing is implied rather than spelled out.

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