Fitbit Heart Rate Intraday

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

Annotations already declare readOnly, idempotent, and non-destructive hints. The description adds meaningful context beyond these: it requires a specific auth scope ('heartrate'), warns about third-party approval, and includes a 'Not medical advice' disclaimer. These are valuable behavioral traits not exposed by annotations, though it doesn't detail response size or pagination (covered by output schema).

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, each earning its place: purpose, usage guidance, and access/disclaimer. It is front-loaded with the core purpose and delivers high information density without fluff.

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 read-only, idempotent data-fetching tool with a rich output schema and strong annotations, the description covers purpose, usage alternatives, auth requirements, and a disclaimer. It doesn't mention rate limits or exact response structure, but the output schema and annotations cover those aspects, making it adequately complete without being exhaustive.

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 67% (4 of 6 parameters have descriptions). The description itself does not elaborate on parameters; however, the two undocumented parameters (detail_level and response_format) have self-explanatory enums. The description adds no meaning beyond the schema, so a baseline score of 3 is appropriate given moderate 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 verb and resource: 'Get raw heart-rate intraday samples for a date.' It clearly differentiates from sibling tools by explicitly naming fitbit_heart_series as the preferred alternative for agent work, leaving no ambiguity about this tool's purpose.

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?

Provides explicit guidance on when to use this tool versus alternatives: 'For agent work prefer fitbit_heart_series (agent-safe-series/v1 with hard point caps and exact stats).' It also notes access limitations ('Personal apps can access their own intraday data; third-party apps may require Fitbit approval'), giving clear contextual usage boundaries.

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