Playwright MCP

browser_press_key

Destructive

Simulate keyboard key presses in web browsers for automated testing or interaction tasks using Playwright MCP server.

Instructions

Press a key on the keyboard

Input Schema

TableJSON Schema

Name	Required	Description	Default
`key`	Yes	Name of the key to press or a character to generate, such as `ArrowLeft` or `a`

Implementation Reference

src/tools/keyboard.ts:37-46 (handler)

Handler function that executes the browser_press_key tool by pressing the specified key on the page using Playwright's keyboard.press method.

  handle: async (tab, params, response) => {
    response.setIncludeSnapshot();
    response.addCode(`// Press ${params.key}`);
    response.addCode(`await page.keyboard.press('${params.key}');`);

    await tab.waitForCompletion(async () => {
      await tab.page.keyboard.press(params.key);
    });
  },
});

src/tools/keyboard.ts:27-35 (schema)

Zod schema definition for the input of the browser_press_key tool, requiring a 'key' string parameter.

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',
},

src/tools.ts:36-52 (registration)

Top-level registration of all tools, including those exported from keyboard.ts (which includes browser_press_key).

export const allTools: Tool<any>[] = [
  ...common,
  ...console,
  ...dialogs,
  ...evaluate,
  ...files,
  ...install,
  ...keyboard,
  ...navigate,
  ...network,
  ...mouse,
  ...pdf,
  ...screenshot,
  ...snapshot,
  ...tabs,
  ...wait,
];

src/tools/keyboard.ts:24-46 (registration)

Definition and local registration of the browser_press_key tool using defineTabTool.

const pressKey = defineTabTool({
  capability: 'core',

  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',
  },

  handle: async (tab, params, response) => {
    response.setIncludeSnapshot();
    response.addCode(`// Press ${params.key}`);
    response.addCode(`await page.keyboard.press('${params.key}');`);

    await tab.waitForCompletion(async () => {
      await tab.page.keyboard.press(params.key);
    });
  },
});

Schema Changelog

Changes observed during successful MCP inspections.

First observedAug 15, 2025

TDQS

B3.3/5.0

Behavior3/5

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

Annotations provide key behavioral hints (destructiveHint: true, readOnlyHint: false, openWorldHint: true), but the description adds minimal context beyond stating the action. It doesn't elaborate on what 'destructive' means in this context (e.g., potential side effects like triggering events) or mention rate limits, though annotations cover the safety profile adequately.

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 with the core action, making it highly efficient and easy to parse, which is ideal for a simple tool.

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 low complexity (1 parameter, no output schema) and rich annotations, the description is minimally adequate. However, it lacks details on return values or error conditions, which could be helpful despite the annotations covering basic behavior.

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?

With 100% schema description coverage, the input schema fully documents the single 'key' parameter, including examples like 'ArrowLeft' or 'a'. The description adds no additional parameter information, so it meets the baseline for high schema 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 resource (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'. It lacks context about specific scenarios, prerequisites, or exclusions, leaving the agent to infer usage from the tool name alone.

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