get_intensity_distribution

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

With no annotations provided, the description carries the disclosure burden. It explains that the tool returns time in heart-rate zones grouped by intensity buckets, includes percentages, and reveals a non-obvious data-quality behavior: it states how many runs have zone detail so an incomplete picture is visible. It does not mention period filtering in prose, but the schema documents the period_days parameter without contradiction.

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 two compact sentences with no wasted words. It front-loads the core output and follows with a useful caveat. Every sentence contributes meaningful information.

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 and only one optional parameter, the description covers the tool's purpose, aggregation scope, and a data-completeness caveat. The only minor gap is not explicitly connecting the result to the period_days window in prose, but the schema handles that detail, making the description nearly complete.

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?

There is only one optional parameter, and schema description coverage is 100%, so the schema already documents period_days with default, minimum, and maximum. The description adds no additional parameter semantics; 'across all runs' could even slightly obscure the period-window behavior, though the schema clarifies it. Baseline 3 is appropriate.

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 clearly identifies the resource (heart-rate zone time across all runs), the output form (percentages), and the organizing question (80/20 polarisation). This is specific enough to distinguish it from siblings like analyze_workout, which targets a single workout, and get_training_load, which is about load rather than zone distribution.

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 explicitly names the use case: it is the basis for the 80/20 polarisation question. This gives an agent a clear trigger for when to use the tool. It does not mention alternatives or exclusion conditions, but the context is strong enough to guide selection.

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