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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, and the description is consistent with them. The description adds that output is an interactive chart plus summary, but provides no further behavioral detail such as authentication requirements or default behavior when no range is supplied. No contradiction exists.

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 a single efficient sentence that front-loads the core purpose and enumerates all valid range options. There is no redundant phrasing or filler.

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?

For a single-parameter, read-only visualization tool with an output schema, the description largely suffices: it names the metric, the range choices, and the return form. It does not say what happens when optional range is omitted, which is a minor but real gap.

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 coverage is 100% for the only parameter, and the range enum is fully documented. The description merely repeats the allowed values (7d, 30d, 90d, 1y) without adding new meaning or clarifying the optional default behavior, so it stays at the baseline for high schema coverage.

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 a specific action and resource: 'Visual resting-heart-rate and HRV trend' and 'Returns an interactive chart plus short summary.' It is clear enough to distinguish from list/log siblings, but it does not explicitly differentiate itself from sibling visualization tools like show_health_overview.

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 implies the intended use case: retrieving a visual RHR/HRV trend over a selected time window. It does not provide explicit when-to-use or when-not-to-use guidance, nor does it mention alternatives, so the agent must infer the right context.

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