Scroll a webpage or a specific element using a CSS selector. Set pixel amount and direction (up, down, left, right) for precise navigation.
Scroll the page, or a specific element when a selector is given.
| Name | Required | Description | Default |
|---|---|---|---|
| amount | No | Pixels to scroll | |
| selector | No | CSS selector of the element to scroll (optional) | |
| direction | No | Scroll direction | down |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
v0.3.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden of behavioral disclosure, but it only restates the core action. It does not describe what happens when the selector is invalid, whether the scroll is animated, or what is returned, though the tool is simple and non-destructive.
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 description is a single sentence with no filler. It front-loads the action and immediately differentiates the two main usage modes, making it easy for an agent to parse quickly.
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?
Given the low complexity, fully documented parameters, and presence of an output schema, the description is mostly complete. It only lacks minor edge-case behavior like error handling for invalid selectors, but that is not essential for basic invocation.
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 the input schema already documents 'amount', 'selector', and 'direction'. The description adds no additional semantic detail beyond the schema, so the baseline score of 3 is appropriate.
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 ('Scroll') and the resource (page or a specific element via selector), clearly identifying the tool's function. Among the sibling browser_* tools, this uniquely describes a scrolling action, so an agent can distinguish it without opening the schema.
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 implies when to use the tool: for scrolling the page or a specific element when a selector is provided. However, it does not explicitly mention alternatives or exclusion cases, such as using browser_evaluate for programmatic scroll or noting that a selector is required for element scrolling.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.