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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description usefully adds the underlying REST endpoint (GET /v2/summary/body/{user_id}), but says nothing about pagination, response size, or whether summarization is daily vs aggregated, which is the kind of context a summary endpoint should disclose.

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 sentences, with the purpose front-loaded ahead of the API breadcrumb. Every clause carries information and nothing is padded.

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 no output schema, the description carries the burden of explaining what a 'body summary' returns (which metrics, granularity, units), and it does not. The parameters and safety profile are adequately covered elsewhere, so the definition is workable but leaves the return shape opaque.

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 100%, so user_id, start_date, end_date, and provider are each documented with type, format, and defaults upstream. The description adds no meaning beyond the schema (it only echoes the date-range concept), so the baseline 3 applies.

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 verb and resource ('Get body summaries') plus the scope ('for a user over a date range'), which separates it from resource-specific siblings like vital_get_sleep and vital_get_activity. It does not, however, draw an explicit line against vital_get_timeseries, which plausibly could return overlapping 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 gives no when-to-use guidance, no prerequisites, and does not name an alternative such as vital_get_timeseries for finer-grained or multi-metric retrieval. The date-range phrasing only implies the calling context that the schema already enforces via required start_date.

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