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Cloudflare Playwright MCP

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by cloudflare

browser_press_key

Destructive

Simulate keyboard key presses in automated browser testing scenarios. Integrate with Cloudflare Playwright MCP to control web browsers for precise interaction testing.

Instructions

Press a key on the keyboard

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
keyYesName of the key to press or a character to generate, such as `ArrowLeft` or `a`

Implementation Reference

  • The handler function for the browser_press_key tool. It presses the specified key on the current tab's page using Playwright's keyboard.press method, generates corresponding code snippet, and returns an action object.
    handle: async (context, params) => {
      const tab = context.currentTabOrDie();
    
      const code = [
        `// Press ${params.key}`,
        `await page.keyboard.press('${params.key}');`,
      ];
    
      const action = () => tab.page.keyboard.press(params.key);
    
      return {
        code,
        action,
        captureSnapshot,
        waitForNetwork: true
      };
    },
  • Schema definition for the browser_press_key tool, including name, title, description, input schema with 'key' parameter validated by Zod, and type 'destructive'.
    schema: {
      name: 'browser_press_key',
      title: 'Press a key',
      description: 'Press a key on the keyboard',
      inputSchema: z.object({
        key: z.string().describe('Name of the key to press or a character to generate, such as `ArrowLeft` or `a`'),
      }),
      type: 'destructive',
    },
  • Exports and registers the browser_press_key tool by including it in the array returned from the tool factory with captureSnapshot parameter.
    export default (captureSnapshot: boolean) => [
      pressKey(captureSnapshot),
    ];
Behavior3/5

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

Annotations provide critical behavioral hints (destructiveHint: true, readOnlyHint: false, openWorldHint: true), which the description doesn't repeat. The description adds minimal context about pressing keys but doesn't elaborate on effects like focus requirements or browser state changes, offering only basic value beyond annotations.

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, clear sentence with zero wasted words. It's front-loaded and efficiently communicates the core action without unnecessary elaboration, 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.

Completeness3/5

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

For a tool with one parameter, full schema coverage, and annotations covering key behavioral traits, the description is minimally adequate. However, it lacks output details (no output schema) and doesn't address sibling tool differentiation, leaving some contextual gaps.

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 the 'key' parameter fully documented in the schema. The description adds no additional parameter information beyond what's in the schema, so it meets the baseline for high coverage without compensating value.

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 'Press a key on the keyboard' clearly states the action (press) and target (key on keyboard), making the purpose immediately understandable. However, it doesn't differentiate from sibling tools like 'browser_type' which might have overlapping functionality, preventing a perfect score.

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 like 'browser_type' or 'browser_click'. There's no mention of context, prerequisites, or exclusions, leaving the agent to guess based on tool names alone.

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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