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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the safety profile is covered. The description adds the returned metric names and the local-date constraint, but says nothing about data availability (e.g. nights with no recording), units, or typical value 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 short sentences with the metric definition front-loaded, then use cases, then the calling constraint. 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 is careful to name the two values returned, which is the key missing piece an agent would otherwise lack. It could still say what happens for nights without data, but it is otherwise sufficient for a single-parameter read tool.

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% and the schema already specifies the YYYY-MM-DD pattern and local-date semantics, so the description's date instruction is largely redundant. Baseline 3 applies since the schema does the heavy lifting.

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 (get) and resource (nightly SpO2 average plus breathing disturbance index) and scopes it to a single date. The named metrics distinguish it cleanly from sibling tools like get_heart_rate_series or get_daily_summary.

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 concrete use cases (altitude effects, suspected sleep apnea, illness tracking), which tells an agent when this tool is the right pick. It stops short of naming alternatives or exclusions, e.g. when to prefer correlate_tag_with_metric or get_daily_summary instead.

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