Polar Heart Series

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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and openWorld, so the safety profile is covered structurally. The description adds real value beyond that: bounded output (500-point cap), a named payload contract ('agent-safe-series/v1'), and a precision/size tradeoff between full-resolution stats and the capped series. It still omits latency, auth requirements, and empty-window behavior.

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 tight sentences with the core purpose front-loaded and the routing hint for polar_daily_summary placed early. The 'Shared contract with garmin/strava/fitbit series tools' line adds cross-tool context at minimal cost, though the jargon-y contract tag is a small readability tax.

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-value explanation is unnecessary, and the read/mutation semantics are covered by annotations. However, for a 5-parameter tool with 20% schema coverage, the description leaves key inputs (resolution_seconds, reference_max_hr) unexplained and never states a when-not-to-use condition.

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 only 20% – essentially just 'date'. The description explains the 500-point ceiling implied by max_points but adds nothing about resolution_seconds, reference_max_hr (used for HR zone context), or response_format. With low coverage, the description should compensate for the undocumented parameters and does not.

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 resource (heart-rate series derived from Polar continuous samples) with a clear scope qualifier ('bounded', 'capped at 500 points') and distinguishes its output model (exact stats on full-resolution samples plus a downsampled series). It does not explicitly name polar_list_continuous_samples as the raw-sample alternative, so sibling differentiation is partial.

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 routing instruction: 'Prefer polar_daily_summary first,' which tells the agent when to reach for another tool before this one. It stops short of stating when this tool is the wrong choice or what conditions require the full series over the summary.

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