screenshot_page

Instructions

Implementation Reference

• src/tools/screenshot.ts:51-66 (handler)

  MCP tool handler: obtains Firefox instance, captures page screenshot via takeScreenshotPage(), validates result, builds formatted response with size checks and truncation if needed.

  export async function handleScreenshotPage(_args: unknown): Promise<McpToolResponse> {
    try {
      const { getFirefox } = await import('../index.js');
      const firefox = await getFirefox();
  
      const base64Png = await firefox.takeScreenshotPage();
  
      if (!base64Png || typeof base64Png !== 'string') {
        throw new Error('Invalid screenshot data');
      }
  
      return buildScreenshotResponse(base64Png, 'page');
    } catch (error) {
      return errorResponse(error as Error);
    }
  }

• src/tools/screenshot.ts:9-16 (schema)

  Tool schema definition: name 'screenshot_page', description, and empty input schema (no parameters required).

  export const screenshotPageTool = {
    name: 'screenshot_page',
    description: 'Capture page screenshot as base64 PNG.',
    inputSchema: {
      type: 'object',
      properties: {},
    },
  };

• src/index.ts:103-147 (registration)

  Registration of screenshot_page handler in the central toolHandlers Map used by the MCP server.

  const toolHandlers = new Map<
    string,
    (input: unknown) => Promise<{ content: Array<{ type: string; text: string }>; isError?: boolean }>
  >([
    // Pages
    ['list_pages', tools.handleListPages],
    ['new_page', tools.handleNewPage],
    ['navigate_page', tools.handleNavigatePage],
    ['select_page', tools.handleSelectPage],
    ['close_page', tools.handleClosePage],
  
    // Script evaluation - DISABLED (see docs/future-features.md)
    // ['evaluate_script', tools.handleEvaluateScript],
  
    // Console
    ['list_console_messages', tools.handleListConsoleMessages],
    ['clear_console_messages', tools.handleClearConsoleMessages],
  
    // Network
    ['list_network_requests', tools.handleListNetworkRequests],
    ['get_network_request', tools.handleGetNetworkRequest],
  
    // Snapshot
    ['take_snapshot', tools.handleTakeSnapshot],
    ['resolve_uid_to_selector', tools.handleResolveUidToSelector],
    ['clear_snapshot', tools.handleClearSnapshot],
  
    // Input
    ['click_by_uid', tools.handleClickByUid],
    ['hover_by_uid', tools.handleHoverByUid],
    ['fill_by_uid', tools.handleFillByUid],
    ['drag_by_uid_to_uid', tools.handleDragByUidToUid],
    ['fill_form_by_uid', tools.handleFillFormByUid],
    ['upload_file_by_uid', tools.handleUploadFileByUid],
  
    // Screenshot
    ['screenshot_page', tools.handleScreenshotPage],
    ['screenshot_by_uid', tools.handleScreenshotByUid],
  
    // Utilities
    ['accept_dialog', tools.handleAcceptDialog],
    ['dismiss_dialog', tools.handleDismissDialog],
    ['navigate_history', tools.handleNavigateHistory],
    ['set_viewport_size', tools.handleSetViewportSize],
  ]);

• src/index.ts:182-191 (registration)

  Inclusion of screenshotPageTool schema in the allTools array for listTools response.

    // Screenshot
    tools.screenshotPageTool,
    tools.screenshotByUidTool,
  
    // Utilities
    tools.acceptDialogTool,
    tools.dismissDialogTool,
    tools.navigateHistoryTool,
    tools.setViewportSizeTool,
  ];

• src/tools/screenshot.ts:36-48 (helper)

  Helper function to format screenshot response with size calculation, truncation for token limits, and emoji/size warnings.

  function buildScreenshotResponse(base64Png: string, label: string): McpToolResponse {
    const sizeKB = Math.round(base64Png.length / 1024);
  
    // Check if screenshot exceeds size limit
    if (base64Png.length > TOKEN_LIMITS.MAX_SCREENSHOT_CHARS) {
      const truncatedData = base64Png.slice(0, TOKEN_LIMITS.MAX_SCREENSHOT_CHARS);
      return successResponse(`📸 ${label} (${sizeKB}KB) [truncated]\n${truncatedData}`);
    }
  
    // Add warning for large screenshots
    const warn = base64Png.length > TOKEN_LIMITS.WARNING_THRESHOLD_CHARS ? ' [large]' : '';
    return successResponse(`📸 ${label} (${sizeKB}KB)${warn}\n${base64Png}`);
  }