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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description still adds useful behavior beyond that: result ordering ('newest first'), the fact that the visit_id mode works 'at any age' outside the window, and the next_cursor pagination loop.

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 purpose and the two modes are front-loaded in the first sentence, and the closing sentence on cursor is actionable. It is dense and slightly run-on with semicolons, but no sentence is redundant filler.

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 10 parameters and no output schema, the description compensates by enumerating the returned fields for both modes ('where they landed and left, their source, country and device' and 'pages, events, referrer'). Filtering and date-window semantics are left to the well-documented schema, which is reasonable at 90% coverage.

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 90%, so the schema already documents nearly every parameter, including cursor ('next_cursor from a previous list') and visit_id ('One visit, from a previous list'). The description largely restates those and only adds the 'at any age' nuance for visit_id, so it does not meaningfully exceed the baseline.

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 and resource ('the visits that started in a window') and distinguishes two modes: a paginated list and a single-visit drill-down selected by visit_id. It also implicitly contrasts itself with the aggregate tools ('Drill below the aggregates'), though it never names a specific sibling like get_breakdown.

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 use-case framing ('For questions like "what did people from X actually do"') and states the pagination workflow ('Pass next_cursor back as cursor for older visits'), which tells the agent how to continue. It stops short of explicit when-not-to-use guidance or naming an alternative tool for aggregate questions.

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