Scroll a specified element into the center of the Firefox viewport using its element reference, making it visible for inspection or interaction.
Scroll an element (by ref) into the centre of the viewport.
| Name | Required | Description | Default |
|---|---|---|---|
| ref | Yes | Element ref from read_page or find, e.g. ref_12 or f1:ref_3 (f1 = inside frame 1) | |
| tabId | Yes | Tab id from tabs_context |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the burden of behavioral disclosure. It clearly states the scroll behavior (centering in viewport), which is useful. However, it doesn't disclose edge cases like whether the scroll is instant/animated, what happens if the element is not found, or whether it affects scrollable containers vs the whole page.
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?
A single, clear sentence that front-loads the action and target. No wasted words; every word earns its place.
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 two-parameter tool with full schema coverage, the description is mostly complete. However, given the sibling 'scroll' tool exists, the description could clarify the distinction (element-level vs page-level scrolling) to prevent mis-selection. No output schema means return behavior is not documented, but for a scroll action this is less critical.
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 schema already documents both parameters. The description adds the behavioral context that the ref is used to identify the element to scroll, but doesn't add meaning beyond the schema's parameter descriptions. Baseline 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 resource ('an element by ref') with a clear target ('into the centre of the viewport'). It distinguishes from the sibling 'scroll' tool by specifying element-level scrolling via ref, though it doesn't explicitly name the sibling or contrast with viewport scrolling.
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 usage: use this when you need to bring a specific element into view, as opposed to general page scrolling. However, it doesn't explicitly state when to use this vs the sibling 'scroll' tool, nor does it mention prerequisites like needing a ref from read_page or find (though the schema hints at this).
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.