get_zone_distribution

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

No annotations are provided, so the description carries the full burden. It usefully discloses the computed output (percentage of time in Z1-Z5 across three sports), but says nothing about permissions, rate limits, or how missing data is handled. The 'get' verb reasonably implies a read operation.

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?

Purpose is front-loaded in the first sentence, with the calculation detail and parameter formats following. The Args block is slightly mechanical but earns its place by supplying the missing date format.

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?

An output schema exists, so return values needn't be explained. For a simple two-parameter read-only aggregate, the description covers purpose, scope, computation, and parameter formats adequately; only usage routing to alternatives 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 description coverage is 0%, so the description must compensate. It does document both required parameters and, importantly, adds the YYYY-MM-DD format the schema omits. Minor gap: no mention of range limits or timezone handling.

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 verb (get) and resource (heart rate zone distribution) with clear scope: across running/cycling/swimming for a date range. This implicitly distinguishes it from per-activity siblings like get_activity_hr_in_timezones, but never names them 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?

The description says what the tool returns but gives no when-to-use guidance, prerequisites, or named alternatives (e.g., vs get_activity_hr_in_timezones for a single activity). Usage must be inferred from scope alone.

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