get_daily_metrics

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

The description provides rich behavioral context: data is served from local SQLite cache, the uncached tail fetches from the API, and longer ranges are chunked into 12-week calls. This goes well beyond the readOnlyHint annotation and clarifies performance and caching 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?

The description is three sentences: a clear purpose statement followed by two sentences of implementation details. Each sentence earns its place, providing useful information without unnecessary verbosity.

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?

Given the output schema exists and annotations indicate read-only behavior, the description fully covers the data source, range constraints, and caching behavior. There are no significant gaps for a single-parameter fetch tool.

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 for the only parameter (weeks) is 100%, so the baseline is 3. The description adds value by explaining that the range is configurable and works even on a cold cache, giving extra confidence about parameter behavior beyond the schema's basic range description.

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 clearly identifies the tool's function: 'Retrieve nightly HRV and daily metrics from Coros' with a configurable time range. It also distinguishes itself from sibling tools like get_sleep_data by specifying 'HRV and daily metrics'.

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 explains how the cache and API are used, implying that the tool is suitable for historical data ranges. However, it does not explicitly mention when to avoid this tool or suggest alternatives, so it lacks explicit exclusion guidance.

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