Move the mouse over an element

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

Adds real behavioral context beyond the single readOnlyHint annotation: it discloses the underlying mechanism (BiDi input.performActions pointerMove) and that the page receives a genuine pointer position rather than a synthetic event, which matters for pages that gate on trusted events. Nothing here contradicts readOnlyHint=false, since hover can trigger menus and stateful UI.

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?

Three tight sentences: purpose first, mechanism second, input rule last. Every clause carries information an agent would otherwise have to infer.

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 five-parameter tool with no output schema, the description covers purpose, mechanism, input modes, and the hover-settling behavior implied by settleMs. It could additionally note what happens on a missing/unmatched selector or whether the pointer position persists, but nothing essential to invoking it is missing.

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 already 100%, so the baseline is 3; the description earns a point by making the selector-vs-coordinate exclusivity explicit and reframing the two modes as a single either/or decision rather than two independent optional fields.

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 ("Move the real mouse pointer onto an element") plus the outcome it enables ("hover-only UI appears: menus, tooltips, :hover styles"). This clearly distinguishes it from siblings like browser_click, browser_mouse_action, and browser_drag.

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?

Gives the triggering conditions well ("hover-only UI," "show on hover" controls) and specifies the input choice: "Give selector OR x/y." It does not, however, contrast itself with near-neighbors such as browser_mouse_action or explain when a hover is insufficient and a click is needed.

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