hrv_night

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

Annotations already establish readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds granularity context (5-minute readings), which is genuinely useful, but says nothing about how many readings come back, what date range a 'night' spans, or what happens when data is missing.

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?

One short sentence with no waste and the key distinguishing detail front-loaded. It reads as a fragment rather than a complete sentence, but nothing is padded.

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 tool with no output schema, the description covers the purpose but leaves the one parameter and the return shape (readings array? timestamps?) entirely unexplained. Adequate as a label, thin as a specification.

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?

The single 'day' parameter has 0% schema description coverage, so the description is the only place that could explain accepted formats ('today', ISO date, relative offsets) — and it never mentions the parameter at all. A caller cannot tell from either source what date syntax is valid.

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?

Names a specific resource (a single night's HRV) and adds a concrete scope detail — it includes the 5-minute readings, which distinguishes it from coarser siblings like daily or readiness_history. The verb is only implied ('in detail'), and no sibling is named explicitly, so it stops short of a 5.

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?

There is no statement of when to use this versus alternatives such as intraday, timeseries, or readiness_history, all of which could plausibly return HRV-adjacent data. The agent must infer from the name alone that this is the single-night, high-resolution option.

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