Get Garmin HRV summaries

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

Beyond the readOnlyHint/openWorldHint annotations, the description discloses units and derivation (milliseconds, RMSSD), the keying convention (wake-up date, which matters for interpreting night boundaries), the returned metric set including the `summary` aggregate, and a hard behavioral limit of 92 nights per call. This is exactly the kind of context annotations cannot carry.

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?

Dense but front-loaded: purpose and returned fields come first, then keying/units, then defaults and limits, then the sibling routing. Every clause carries information and nothing is repeated verbatim from the schema.

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 takes on the burden of describing returns and does so concretely, down to the status enum values and the `summary` aggregates. Together with defaults, the 92-night cap, and unit disclosure, an agent has everything needed to call and interpret this tool correctly.

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 description coverage is 100%, and both parameters are documented there including their defaults and the 92-day cap, so the description's 'Defaults to the last 7 nights; at most 92 nights per call' largely restates the schema. The only added interpretive value is the wake-up-date framing, which concerns result semantics rather than the parameters themselves. Baseline 3 applies.

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?

The description states a specific verb and resource ('Overnight heart-rate variability per night over a date range') and enumerates what comes back (last-night average, 5-minute high, 7-day average, baseline range, HRV status). It explicitly distinguishes itself from the near-identical sibling garmin_get_hrv, so an agent can choose without opening either 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?

It gives a clear selection rule: use this for trends across nights, and use garmin_get_hrv for a single night with overnight readings. That is an explicit alternative with a condition. It stops short of exclusions against adjacent wellness tools (sleep, stress, body battery), so it is strong but not exhaustive.

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