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

Annotations already establish read-only, non-destructive and idempotent, so safety is covered. The description adds real behavioral context beyond that: results are ordered newest first, cursoring via next_cursor walks toward older visits, and visit_id retrieves a visit 'at any age' regardless of window. It does not discuss rate limits or response size, but the ordering and pagination semantics are the important disclosures.

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 core capability is front-loaded in the opening clause ('Drill below the aggregates'), followed by a compact enumeration of returned fields and a short pagination note. The main sentence is dense and long, but every clause carries information an agent needs to choose a mode.

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 eight parameters and no output schema, the description has to convey what comes back, and it does: per-visit landing/exit, source, country and device for lists, and pages, events and referrer for a single visit. Both invocation modes are covered, so an agent can call it correctly without further documentation.

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 88%, so the baseline is 3. The description still adds meaning the schema does not spell out, notably that visiting by visit_id is not bound to the date window ('at any age') and that the cursor exists specifically to fetch older visits. The from/to/period interplay is left to the schema, which already documents the override.

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 states a specific verb and resource ('the visits that started in a window, newest first'), and it explicitly positions the tool below the aggregates, which separates it from siblings like get_breakdown, get_overview and get_timeseries. It also names the record-level fields returned (landing/exit, source, country, device) and the second mode keyed by visit_id.

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?

It gives a concrete selection cue: use this when the question is 'what did people from X actually do', i.e. when aggregate breakdowns are not enough. The two modes (window listing vs single-visit drilldown via visit_id) have clear triggers. It stops short of explicit when-not guidance or naming a sibling alternative by name.

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