Browser Use Server

Instructions

Implementation Reference

• src/browser_handler.py:222-248 (handler)

  Handler for the 'execute_js' command. Navigates to the specified URL using an AI agent for optional steps, then executes the provided JavaScript script on the page and returns the result.

  elif command == 'execute_js':
      if not args.get('url') or not args.get('script'):
          return {
              'success': False,
              'error': 'URL and script are required for execute_js command'
          }
  
      task = f"1. Go to {args['url']}"
      if args.get('steps'):
          steps = args['steps'].split(',')
          for i, step in enumerate(steps, 2):
              task += f"\n{i}. {step.strip()}"
          task += f"\n{len(steps) + 2}. Execute JavaScript: {args['script']}"
      else:
          task += f"\n2. Execute JavaScript: {args['script']}"
      use_vision = os.getenv('USE_VISION', 'false').lower() == 'true'
      agent = Agent(task=task, llm=llm, use_vision=use_vision, browser_context=context)
      await agent.run()
  
      try:
          result = await context.execute_javascript(args['script'])
          return {
              'success': True,
              'result': result
          }
      finally:
          await context.close()

• src/index.ts:192-212 (registration)

  Registration of the 'execute_js' tool in the MCP server, including name, description, and input schema definition.

  {
    name: 'execute_js',
    description: 'Execute JavaScript code on a webpage',
    inputSchema: {
      type: 'object',
      properties: {
        url: {
          type: 'string',
          description: 'The URL to navigate to',
        },
        script: {
          type: 'string',
          description: 'The JavaScript code to execute',
        },
        steps: {
          type: 'string',
          description: 'Comma-separated actions or sentences describing steps to take after page load (e.g., "click #submit, scroll down" or "Fill the login form and submit")',
        },
      },
      required: ['url', 'script'],
    },

• src/index.ts:252-257 (schema)

  Input validation specifically for the 'execute_js' tool, ensuring the script argument is a string.

  if (request.params.name === 'execute_js' && typeof args.script !== 'string') {
    throw new McpError(
      ErrorCode.InvalidParams,
      'Script must be a string'
    );
  }

• src/browser_handler.py:242-248 (helper)

  Core execution of the JavaScript using the browser context's execute_javascript method.

      result = await context.execute_javascript(args['script'])
      return {
          'success': True,
          'result': result
      }
  finally:
      await context.close()