Get Garmin heart-rate zones

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

readOnlyHint=true and openWorldHint=false already establish a safe, local read, so the description's job is to say what comes back - and it does, naming zone bpm ranges, max/resting/lactate-threshold values, the calculation method, and the per-sport grouping. It does not say anything about sport coverage (which activities have zones) or behavior when no zones are configured, which is a modest gap below a 5.

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 sentences, zero waste. The payload (what the zones contain) is front-loaded and the sibling disambiguation follows it, which is the correct priority order.

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 parameters and no output schema, the description carries the full burden of describing the return shape, and it does so by enumerating the zone ranges, the three reference heart rates, and the derivation method. Nothing an agent needs in order to call or interpret this tool 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?

The tool takes zero parameters, so there is nothing for the description to disambiguate beyond confirming the call is argument-free, which matches the empty schema. Baseline 4 applies for a no-parameter tool.

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 (heart-rate zones per sport) and enumerates its contents: bpm ranges for zones 1-5 plus max, resting and lactate-threshold heart rate and the method they are based on. That precision, plus the explicit contrast with garmin_get_profile, lets an agent distinguish it from every sibling without opening a 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?

The second sentence routes the agent: garmin_get_profile returns the same zones together with profile settings, implying this tool is the narrower choice when only zones are needed. The guidance is clear but implicit - it never states an explicit 'use this when' / 'use profile when' condition, which is the only thing separating it from a 5.

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