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

Annotations already declare readOnly/idempotent/non-destructive, and the description reinforces that with 'Read-only; changes nothing.' The genuinely additive detail is that the supplied examDate is not persisted — important because the sibling save_study_settings does save a date, so this prevents an agent from assuming a write. It stops short of describing plan length or output volume for long date ranges.

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?

Three sentences, front-loaded with the core action, then the date-default rule, then the read-only guarantee. Slightly dense — the first sentence carries a long clause list — but every sentence contributes a distinct fact with no filler.

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 no output schema, the description carries the burden of hinting at what comes back, and it does so by naming the plan's components (daily practice, missed-problem review, timed sets, rest days). Both optional parameters and the defaulting rule are covered; only the shape/size of the returned plan is left unstated.

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 100%, so the baseline is 3, but the description goes beyond the schema by explaining the relationship between the two parameters: exam defaults to the saved grade, and examDate overrides the saved date without being written back. That override/non-persistence semantics is real added meaning not present in the field descriptions.

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 — 'Build a day-by-day math study plan for one exam (grade) up to the exam date' — and enumerates what the plan contains (weak-topic weighting, missed-problem review, timed sets, rest days). It also differentiates itself from save_study_settings (saves the date) and get_exam_overview (lists grade ids), so an agent can distinguish it without opening the 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 clear context for the two modes: default to the date saved in WaterExamMath for that grade, or pass examDate to plan against a different date. It names sibling tools as the source of defaults/ids, but it never states an explicit 'do not use this when…' exclusion, so the alternative-selection guidance is implied rather than complete.

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