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browser_resize

Destructive

Adjust browser window dimensions for testing responsive web designs or capturing specific viewport states by setting width and height parameters.

Instructions

Resize the browser window

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
widthYesWidth of the browser window
heightYesHeight of the browser window

Implementation Reference

  • The main handler function for the 'browser_resize' tool. It validates input parameters using resizeSchema, retrieves the current tab from context, resizes the viewport using tab.page.setViewportSize, generates a code snippet for the action, and returns it within tab.run.
      handle: async (context, params) => {
        const validatedParams = resizeSchema.parse(params);
    
        const tab = context.currentTab();
        return await tab.run(async tab => {
          await tab.page.setViewportSize({ width: validatedParams.width, height: validatedParams.height });
          const code = [
            `// Resize browser window to ${validatedParams.width}x${validatedParams.height}`,
            `await page.setViewportSize({ width: ${validatedParams.width}, height: ${validatedParams.height} });`
          ];
          return { code };
        }, {
          captureSnapshot,
        });
      },
    });
  • Zod schema for validating input parameters of browser_resize: width and height as numbers with descriptions.
    const resizeSchema = z.object({
      width: z.number().describe('Width of the browser window'),
      height: z.number().describe('Height of the browser window'),
    });
  • Registration of the browser_resize tool via the resize factory function in the exported array of common tools.
    export default (captureSnapshot: boolean) => [
      close,
      wait,
      resize(captureSnapshot)
    ];
Behavior3/5

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

Annotations indicate destructiveHint=true and readOnlyHint=false, which the description doesn't contradict (it implies a mutation). The description adds minimal behavioral context beyond annotations, as it doesn't specify effects like window state changes or potential visual disruptions. With annotations covering safety, it meets a baseline but lacks details on rate limits or system impacts.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, efficient sentence that directly states the tool's function without unnecessary words. It's front-loaded and wastes no space, making it easy to parse quickly. Every part of the sentence earns its place by conveying the core action.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's moderate complexity (a destructive operation with two parameters), annotations provide safety info, but there's no output schema. The description is minimal and doesn't cover return values or error conditions. It's adequate for basic understanding but lacks depth for full contextual use.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, with clear descriptions for width and height parameters. The description doesn't add meaning beyond the schema, such as units (pixels), valid ranges, or default behaviors. Baseline score of 3 is appropriate since the schema handles parameter documentation adequately.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb ('Resize') and resource ('the browser window'), making the purpose immediately understandable. It doesn't explicitly differentiate from siblings like browser_close or browser_snapshot, but the action is distinct enough in context. The description avoids tautology by not just restating the name/title.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing an active browser session), exclusions (e.g., not for mobile browsers), or sibling tools that might be related (like browser_snapshot for capturing after resize). Usage is implied from the action alone without context.

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

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