Fitbit Demo

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

Annotations already declare readOnlyHint, destructiveHint, and idempotentHint. The description adds value by clarifying that it returns example payloads rather than real data, which is important behavioral context beyond what annotations provide. No contradictions.

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 a single 19-word sentence that clearly states purpose and makes every word count. It is front-loaded with the key action and immediately specifies the target tools.

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 simple demo tool with good annotations, the description explains the main purpose and return type. However, the complete omission of parameter documentation leaves a significant gap, and the description does not mention the absence of real data effects (though annotations cover idempotency).

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 schema has 0% description coverage for the single parameter (response_format), and the tool description does not mention or explain it. The agent has no way to know what the parameter does or which value to choose, despite an enum defaulting to 'markdown'.

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 explicitly states it returns realistic example payloads for three named tools (fitbit_daily_summary, fitbit_wellness_context, fitbit_get_heart_day) to let agents see the contract before calling real APIs. This clearly distinguishes it from sibling tools that return actual data.

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 implies usage before calling real Fitbit APIs, saying 'so agents see the contract before calling real Fitbit APIs.' However, it lacks explicit guidance on when not to use it or mention of alternative tools (e.g., the real data endpoints themselves).

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