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

Annotations already cover read-only and non-destructive safety. The description goes well beyond them: newest-first ordering, page-until-`has_more`-is-false semantics, and the important caveat that values withheld by a device maker return empty with a `restriction` field and must not be treated as missing data.

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-loads the what, then a compact parameter block, then the caveat. Every sentence carries operational information; no filler or restatement of the title.

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?

Output schema exists so return shape needn't be explained, and the description still covers the two things an agent would otherwise get wrong: how to paginate and how to interpret empty-with-restriction results. Nothing needed to call this correctly 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 0%, yet the description documents every parameter: `mti_…` handle format for metric, `usr_…` handle for athlete, 'YYYY-MM-DD' for the date window, `limit` capped at 100, and `starting_after` taking the last returned `id`. It fully compensates for the empty schema 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 ('Read the daily values of a metric') and enumerates example metrics (HRV, resting heart rate, sleep, weight, Hooper). It is clearly separable from the sibling list_metrics, which supplies the metric handles rather than the values.

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?

Explicitly tells the agent to omit `metric` for all metrics and omit `athlete` for its own values, and routes handle lookup to list_metrics. It gives clear context for each parameter but states no exclusions or when-not-to-use conditions versus other read siblings like get_records.

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