fitbit_get_heart_rate

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

With no annotations provided, the description carries the full burden. It discloses that data comes 'from the local cache by default, auto-syncing if stale' and that live=True fetches directly from Fitbit, plus it outlines the daily return structure. It doesn't mention auth/rate limits, but the key behavioral traits are well covered.

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 well-structured and front-loaded with a one-sentence summary followed by cache/live details, Args, and return format. Every sentence adds value; no fluff or repetition.

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?

Despite having an output schema, the description still explains the return shape (one entry per day, resting_hr, zones array with name/minutes/caloriesOut/min/max). It provides all needed context for dates, caching, and live mode, making this a fully self-contained description.

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%, and the description fully compensates. It explains start_date formats ('YYYY-MM-DD', 'YYYY-MM', or '30d'), defaults, end_date default, and the live flag's effect, adding meaning far beyond the bare schema properties.

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 opens with a specific verb+resource: 'Get daily resting heart rate and heart rate zones.' It clearly distinguishes this tool from siblings like fitbit_get_hrv or fitbit_get_breathing_rate by naming the exact data returned (resting HR and zone breakdown).

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 clearly explains cache behavior and when to use live=True ('Use live=True to bypass the cache entirely'), plus date format options. It does not explicitly mention alternatives among sibling tools, but the cache-vs-live guidance provides clear contextual usage.

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