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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, but the description adds value the annotations don't: this is account-level scoped and irreversible ('not undoable'), which is critical context for a mutation. It does not disclose auth requirements or what is returned, but with annotation coverage the bar is lower.

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 the core action, which is good, but the closing clause ('not meant for an account that is already set up' / 'not intended for an already-configured account') restates the same exclusion twice, wasting space in an otherwise short description.

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 3-param, no-output-schema, one-shot account initializer, the description covers the essentials an agent needs: irreversibility, account-level scope, the not-already-set-up precondition, and the companion settings call. Missing only parameter units and any error/conflict behavior on return.

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 only 33% (only periodStartDate is documented), so the description must compensate. It does add real meaning — periodStartDate is the *first* period start and the two lengths are *averages* — but it never states units (days?) or plausible ranges for periodLength/cycleLength, leaving the two undocumented numeric params ambiguous.

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 specific verb and resource ('Sets up cycle tracking') plus the exact inputs it seeds the setup from (first period start date, average period/cycle lengths). An agent can distinguish it from siblings like confirm_menstrual_period_start and update_menstrual_settings without opening any schema.

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 when-not ('not meant for an account that is already set up') and names the alternative for the adjacent task ('call updateMenstrualSettings separately' for tracking preferences). The agent is told both the exclusion condition and the correct sibling to route to.

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