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

Annotations cover the safety profile (readOnly, openWorld), and the description adds genuinely useful operational behavior beyond them: the 28-day-per-request limit, automatic chunking, de-duplication by calendarDate, and sorting. It stops short of noting latency/rate implications of large ranges, but the disclosure is well above the annotation baseline.

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 purpose, then the operational caveat. The chunking behavior is stated twice ('ranges over 28 days are fetched in chunks' and '28-day-per-request limit... auto-chunked'), which is mild redundancy but the sentences otherwise earn their place.

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 read-only two-date-range tool with full schema coverage, complete annotations, and no output schema, the description is sufficient: an agent knows what it returns (per-night stats), what it accepts, and the range behavior. Only the relationship to get_sleep_data is missing.

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% with both date parameters fully documented as YYYY-MM-DD UTC, so the schema carries parameter semantics. The description frames them as a date range but adds no format or edge-case detail beyond the schema, matching the baseline for high coverage.

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+resource+granularity: 'Per-night sleep stats over a date range.' The 'per-night' qualifier implies daily aggregation, which hints at differentiation from the sibling get_sleep_data, but that sibling is never named, so the distinction must be inferred.

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?

Usage is only implied through 'over a date range' plus the note that large ranges are chunked, which tells the agent it is safe to pass wide ranges. No when-to-use vs when-not, and the obvious alternative (get_sleep_data) is not mentioned, leaving selection to inference.

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