chart

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds useful behavioral details: the output is an image, the panel cap is 6, and certain metrics get special rendering. It stops short of stating the return mechanism (image content vs. path), the failure mode when more than 6 metrics are supplied, or how the rolling mean window is chosen.

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 output format is front-loaded in the first clause, and rendering rules follow logically. The example metric sets are dense but genuinely informative rather than filler. Slightly list-heavy, but no sentence is wasted.

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 0% schema coverage, no output schema, and four parameters, the description should define the time-window (days/end) and smoothing semantics, plus valid metric names (perhaps pointing at list_metrics). It covers only the panel limit and rendering style, so an agent cannot confidently set the date range or smoothing window from the definition alone.

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 all four parameters (end, days, smooth, metrics) rely entirely on the description for meaning. The description only addresses metrics (max 6) and alludes to the rolling mean without naming or quantifying the 'smooth' parameter. days and end — the entire time window control — are never mentioned, leaving the agent to guess defaults and formats.

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 precisely what is produced: a PNG chart of up to 6 daily metrics rendered as stacked panels on a shared date axis, with points/bars for raw values and a line for the rolling mean. This clearly distinguishes it from data-returning siblings like timeseries and dashboard_data. Metric-specific rendering notes (HRV balanced band, readiness_est showing Garmin scores) further pin down the output.

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 'Good sets' examples give concrete usage hints about which metrics combine sensibly, which is real guidance beyond the schema. However, it never says when to pick chart over timeseries, dashboard_data, or weekly_report, nor any exclusions (e.g. what happens above 6 metrics). Usage is implied rather than stated.

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