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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds two useful notes beyond that: results are 'calculated' (derived, not raw samples) and are 'subject to sharing permissions'. However it says nothing about what the comparison object looks like or how missing/permission-restricted metrics are represented.

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?

A single front-loaded sentence that leads with the action and the comparison window, then lists the covered metrics, then closes with the permission caveat. No filler, no repetition of the name or 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?

For a zero-parameter, read-only tool with annotations carrying the safety profile, the description defines scope and caveats adequately. The one gap is return shape: there is no output schema, so a brief note on how the comparison is presented (e.g. deltas or per-metric pairs) would help an agent interpret results.

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?

The tool takes zero parameters, so the baseline is 4. The description correctly implies there is nothing to configure: the time window is fixed at seven days versus the preceding seven, which tells the agent no date arguments are needed.

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 a calculated comparison of the last seven days with the preceding seven') and enumerates the metrics covered: steps, energy, exercise, sleep, resting heart rate, HRV, workout totals. The fixed 7-vs-7 window distinguishes it from siblings like get_daily_metrics, though no sibling is named explicitly.

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?

No explicit when-to-use or when-not-to-use guidance, and no alternatives are named. Usage is only implied by the description's scope: this is the tool for week-over-week comparison, whereas get_daily_metrics covers single days. An agent must infer that routing itself.

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