get_hrvRetrieve one night's HRV summary and individual readings for a specific date or today/yesterday, useful when the raw readings matter rather than only summaries.
HRV summary plus individual readings for one night. Use get_hrv_summaries unless the readings themselves matter.
| Name | Required | Description | Default |
|---|---|---|---|
| date | Yes | YYYY-MM-DD, or 'today' / 'yesterday' (resolved in the user's Garmin time zone). |
Changes observed during successful MCP inspections.
v1.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The annotations already declare readOnly, idempotent, openWorld, and non-destructive, so safety is covered. The description adds that the response contains both a summary and per-reading values, which is useful since there's no output schema, but it says nothing about reading granularity, units, empty-night behavior, or result size.
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?
Two short sentences, zero filler. The resource and return shape come first, and the disambiguation against the sibling follows immediately.
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 single-parameter read tool with full annotation coverage and no output schema, the description does the essential job: it says what comes back and how it differs from the aggregate sibling. Only minor gaps remain, such as what a 'reading' represents or what happens when no data exists for the night.
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 the single 'date' parameter is fully documented in the schema, including the 'today'/'yesterday' tokens and time-zone resolution. The description's 'one night' phrasing reinforces that this is a per-night lookup but adds no format detail beyond the schema.
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 names the resource precisely ('HRV summary plus individual readings for one night') and distinguishes it from the sibling get_hrv_summaries by saying the readings themselves are what differ. It lacks an explicit verb like 'retrieve', but the scope is unambiguous.
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 names the alternative (get_hrv_summaries) and states the exact condition that selects this tool instead: only when the individual readings matter. This is a textbook when-to-use/when-not-to-use statement.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.