Adjust the browser viewport size and device scale factor to control content display and scaling for responsive design testing.
Change the browser's viewport size and scale factor
| Name | Required | Description | Default |
|---|---|---|---|
| width | No | Viewport width in pixels | |
| height | No | Viewport height in pixels | |
| deviceScaleFactor | No | Device scale factor (affects how content is scaled) |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations exist, so the description should disclose behavioral traits. It only states what the tool changes, but not side effects (e.g., impact on screenshots, persistence across navigation). Lacks important context for a mutation tool.
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?
Single sentence, no fluff. Every word is relevant. Excellent conciseness.
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?
Adequately describes the core function, but lacks details on required fields, defaults, or behavioral context. Acceptable for a simple tool, but could be more complete.
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 100%, with meaningful descriptions for each parameter. The description adds no extra meaning beyond the schema, justifying the baseline score.
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?
Description clearly states the action 'Change' and the target 'browser's viewport size and scale factor'. It is specific and distinct from sibling tools like browser_navigate or browser_click.
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?
No explicit when-to-use guidance is provided. The description implies usage for adjusting viewport, but does not mention alternatives or exclusions. Minimal viable score.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.