Heart rate variability

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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is established. The description adds some context by scoping to overnight data and naming the three output dimensions, but it does not disclose behavioral traits such as data availability limitations, how 'status' is derived, or how missing nights are handled. This is acceptable given annotation coverage but not rich.

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?

The description is a single, front-loaded sentence with no filler. Every word earns its place by conveying the data scope and the specific metrics, making it easy for an agent to parse quickly.

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?

Given the low complexity (one optional parameter), the annotations, and the presence of an output schema, the description is reasonably positioned but not fully complete. The main gap is the undefined date parameter and the absence of any usage guidance, which are not compensated by the existing structured metadata.

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 0% and the description never mentions the 'date' parameter. The phrase 'last-night' loosely implies the date refers to the night of interest, but there is no explicit explanation of what date means, the expected format, or what null/default behavior does. With a single optional parameter, the description should compensate by clarifying its semantics.

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 a specific resource and scope: overnight heart rate variability, with the relevant metrics (last-night average, baseline, status). It clearly identifies what the tool is about, though it uses a noun phrase rather than an explicit verb like 'get' or 'retrieve' and does not explicitly differentiate it from sibling tools such as garmin_heart_rate.

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?

The description provides no guidance on when to use this tool versus alternatives, no exclusions, and no conditions. While the metric name implies a use case, the agent is given no explicit information about when to choose garmin_hrv over garmin_heart_rate, garmin_training_readiness, or garmin_stress.

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