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

The annotation readOnlyHint=true already establishes the safe read-only nature, and the description's 'GET' and 'Get' wording is consistent with that. It adds the date-range scoping and endpoint, but does not describe return format, pagination, or provider-dependent behavior.

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, front-loaded sentences; the action and resource come first, and the API endpoint is a useful, non-redundant addition. No filler or repetition of schema content.

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 read-only retrieval with well-documented parameters and a readOnlyHint, the description is mostly complete. It lacks output-format detail, but the endpoint and 'activity summaries' phrasing give enough context to select and call it correctly.

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 already documents all four parameters at 100% coverage, so the baseline is 3. The endpoint template adds value by showing that user_id is a path parameter rather than a query/body field, which the schema alone does not convey.

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 names the resource ('activity summaries') and action ('Get') for a user over a date range, and even includes the exact API endpoint. It does not explicitly differentiate from siblings like vital_get_workouts or vital_get_timeseries, so it stops short of a 5.

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?

No guidance is given about when to choose this tool over the many sibling getters, nor any exclusions or alternatives. The only implied trigger is the tool name itself, which is not enough.

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