Icu Get Pace Histogram

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower; the description still adds scope detail not in annotations — analysis is confined to a single activity and returns bucketed time-in-zone rather than summary values. It does not say anything about bucket resolution, zone boundaries, or behavior for activities lacking pace data, so it falls short of 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?

Four short sentences, zero filler, with the core definition front-loaded and differentiation/routing trailing. Each sentence carries distinct information: what it is, how it differs, when to use it, and the GAP alternative.

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 covering the return format and annotations covering safety, the description supplies the remaining essentials: single-activity scope, distribution semantics, and sibling routing. Minor gaps remain around what happens when pace data is absent or how buckets are defined, but nothing critical 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?

Only one parameter exists and schema coverage is 100%, so the schema already documents activity_id fully. The description reinforces scope ('within a single running activity') but adds no format, ID-source, or constraint details beyond that, so the 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?

States a specific verb+resource: 'Time-in-zone DISTRIBUTION of pace within a single running activity,' and clarifies the return shape (histogram buckets, time per bucket). It explicitly distinguishes itself from two siblings (icu_get_pace_curves, icu_get_gap_histogram), so an agent can select it without opening any 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?

Gives an explicit when-to-use ('pace-distribution / consistency analysis'), names the scoping difference from icu_get_pace_curves (one activity vs many), and routes elevation-normalized use to icu_get_gap_histogram. Both alternatives and the condition selecting each are spelled out.

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