fitbit_summary

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

Goes well past the annotations (readOnly/openWorld/non-destructive) by disclosing the 1-14 day window, end-exclusive interval semantics, wake-date grouping for sleep, explicit surfacing of missing/conflicting/partial/failed data, and the rule that totals are null unless every requested day is observed. Those aggregation and data-quality semantics materially change how results should be interpreted.

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?

Four short sentences, each carrying distinct information with no filler, and the core scope is front-loaded. It is dense but not padded; minor jargon ('civil days', 'reconciles wearable sources') slightly raises parsing cost.

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?

With readOnly annotations covering the safety profile and no output schema to defer to, the description supplies the semantics an agent actually needs: interval rules, data-quality guarantees, and the null-totals condition. The only meaningful gap is that the domains selector and resulting response shape are never described.

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 coverage is 0% and the description does explain the two date parameters (range limit, end-exclusive behavior), which compensates for the most important ones. The domains parameter and its activity/sleep/heart enum are not mentioned at all, so coverage of the three parameters is only partial.

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?

States a specific deliverable: normalized daily health metrics plus period statistics over a bounded date range, which is clearly distinct from raw-read siblings like fitbit_activity or fitbit_read. It never names a sibling or explicitly contrasts itself, so an agent must infer the boundary.

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?

Usage is only implied by the description of outputs ('daily health metrics and period statistics for 1-14 civil days'); there is no when-to-use statement, no exclusion, and no pointer to fitbit_activity or fitbit_compare as alternatives. Adequate for a capable agent but leaves routing to inference.

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