fitbit_get_azm

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

With no annotations, the description carries the full burden and does so thoroughly. It discloses the caching behavior ('Returns from local cache by default, auto-syncing if stale'), the option to bypass via live=True, and the exact return shape (per-day total_minutes and per-zone breakdown). It even notes the double-counting rule for Cardio/Peak zones, which is a non-obvious behavioral detail.

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-organized with a title, a brief explanation, an Args section, Returns section, and a sibling distinction. Every sentence adds value; there is no fluff. It is appropriately sized for the tool's complexity.

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?

The description is complete given the tool's context: it explains the metric, the return format, cache behavior, and the distinction from a similar sibling. An output schema exists, but the description still adds valuable context about the per-zone breakdown. No gaps are apparent.

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?

Despite 0% schema description coverage, the description fully documents all three parameters: start_date (formats and default), end_date (format and default), and live (purpose). It also clarifies the return semantics, which is beyond the schema. This compensates completely for the schema's lack of info.

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 Active Zone Minutes (AZM)' and clearly distinguishes this from the sibling fitbit_get_activity by explaining the difference in what each metric counts (zone minutes vs wall-clock minutes). This makes the purpose unequivocal.

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 provides explicit usage context: when to use live=True vs the default cache, and explicitly contrasts with fitbit_get_activity ('Distinct from active_minutes...'). It also explains the date range defaults, giving clear guidance on when to invoke this tool over alternatives.

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