get_trends

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

The annotations already declare this as a read-only, idempotent, non-destructive operation, so the safety profile is covered. The description adds useful behavior by naming the aggregate statistics and noting that percent change is returned 'where possible,' but it does not mention rate limits, permission requirements, or result-shape caveats beyond that.

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 front-loaded sentence with no wasted text. The purpose and returned statistics are expressed efficiently.

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 six-parameter aggregation tool with no output schema, the description is minimally adequate: it says what is calculated but not how the time window, source filter, timezone, or deduplication affect results. Some parameter details are covered by the schema and safety is covered by annotations, but meaningful gaps remain.

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 only 50%, and the description does not compensate for the undocumented parameters such as days, timezone, and data_types. It also does not explain how source_priority or deduplicate affect the calculation, leaving most parameter meaning to the schema or inference.

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 uses a specific verb (Calculate) and resource (numeric trend summaries) and enumerates the summary statistics returned. It is clear what the tool does, but it does not distinguish itself from similar siblings such as get_metrics or get_recent_metrics, and it says 'Fitbit metrics' even though the source enum includes HEALTH_KIT and all.

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 gives no explicit when-to-use guidance, prerequisites, or alternatives. It implies the tool is for trend summaries but does not tell an agent when to choose it over get_metrics, get_recent_metrics, or get_health_snapshot.

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