get_heart_rate

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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuinely non-obvious behavioral context: results are informational not medical, and missing Garmin fields are returned as the literal string 'not recorded' and must not be coerced to zero — a real correctness hazard the agent otherwise could not know.

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?

Three tight sentences, front-loaded with the returned fields before the caveats. The only wasted element is the unexplained 'T5.' prefix, which costs a little clarity without earning space.

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 an output schema present, the description need not explain return values, and it does cover the two things an agent must know: the informational disclaimer and the null-sentinel semantics. It does not address how the single date is interpreted (timezone/local day), a minor remaining gap for a daily-metric tool.

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?

Only one parameter, and the schema already documents it fully at 100% coverage with format and example. The description's phrase 'one day's' usefully confirms the date is a single day rather than a range, but adds no further syntax or formatting meaning.

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 resource (one day of heart rate data) and enumerates exactly what is returned (resting, min, max, 7-day resting average, plus heart rate zones), which distinguishes it from get_hrv and get_daily_overview. It does not explicitly name a sibling tool to route away from, and the leading 'T5.' token is opaque to an agent.

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?

'One day's heart rate' implies a single-date scope, and the 'not recorded' caveat tells an agent how to interpret results, but there is no explicit statement of when to prefer this over get_daily_overview or get_hrv. Usage is inferable rather than stated.

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