HRV

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

Annotations already declare read-only, idempotent, non-destructive behavior, so the bar is lower. The description still adds non-obvious operating context: long ranges are auto-chunked and capped at 366 days, which an agent needs to know before requesting wide spans.

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, front-loaded with the payload contents, then the one operational caveat about chunking. No redundant restatement of the tool name or 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 usefully enumerates the returned metric fields and the chunking/cap behavior. Minor gap: it does not state units or what 'baseline range' looks like, but nothing essential to correct invocation 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 100%, so start_date/end_date formats and defaults are fully documented in the schema. The description adds only the max-span constraint (366 days), which is a marginal but real contribution — 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?

States a specific resource (per-night HRV) and enumerates exactly what is returned: last-night average, weekly average, baseline range and status. It is clearly distinguishable from siblings like garmin_get_sleep or garmin_get_stress by resource, though it never names an alternative 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?

Usage is implied by the described payload — an agent can infer it should call this when it needs HRV status — but there is no explicit when-to-use/when-not guidance or comparison to garmin_get_heart_rate or garmin_get_performance_metrics.

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