Fitbit Daily HRV

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

Annotations declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive. The description adds behavioral context about required scope and device support, plus the non-medical disclaimer. No contradiction with annotations.

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?

Two short, efficient sentences. The first sentence states the purpose, the second adds constraints. No wasted words or redundant information.

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 presence of detailed annotations and an output schema (not shown), the description covers essential context: purpose, prerequisites, disclaimer. It lacks explanation of return values, but the output schema likely covers that. Adequate for a simple tool with few parameters.

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 description does not add any parameter meaning beyond the input schema. Schema covers 2 of 3 parameters with descriptions (date and privacy_mode), but the third parameter (response_format) lacks a schema description and is not mentioned in the tool description. The description fails to compensate for this gap.

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 states 'Get HRV summary for a date' with a specific verb and resource. The name and title align, and the mention of HRV distinguishes it from sibling tools like fitbit_get_sleep_day or fitbit_get_heart_day.

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 prerequisites (heartrate scope, supported device/data) and a disclaimer (not medical advice), giving the agent context for when to use the tool. It lacks explicit alternatives or when-not-to-use guidance, but the prerequisites are clear.

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