firefox-devtools-mcp

Instructions

Implementation Reference

• src/tools/input.ts:28-45 (schema)

  Tool schema definition with name 'click_by_uid', description, and input schema requiring 'uid' (string) and optional 'dblClick' (boolean).

  export const clickByUidTool = {
    name: 'click_by_uid',
    description: 'Click element by UID. Set dblClick for double-click.',
    inputSchema: {
      type: 'object',
      properties: {
        uid: {
          type: 'string',
          description: 'Element UID from snapshot',
        },
        dblClick: {
          type: 'boolean',
          description: 'Double-click (default: false)',
        },
      },
      required: ['uid'],
    },
  };

• src/tools/input.ts:149-169 (handler)

  MCP tool handler: validates arguments, imports and calls getFirefox(), executes firefox.clickByUid(uid, dblClick), handles UID errors with user-friendly messages, returns success or error response.

  export async function handleClickByUid(args: unknown): Promise<McpToolResponse> {
    try {
      const { uid, dblClick } = args as { uid: string; dblClick?: boolean };
  
      if (!uid || typeof uid !== 'string') {
        throw new Error('uid parameter is required and must be a string');
      }
  
      const { getFirefox } = await import('../index.js');
      const firefox = await getFirefox();
  
      try {
        await firefox.clickByUid(uid, dblClick);
        return successResponse(`✅ ${dblClick ? 'dblclick' : 'click'} ${uid}`);
      } catch (error) {
        throw handleUidError(error as Error, uid);
      }
    } catch (error) {
      return errorResponse(error as Error);
    }
  }

• src/index.ts:130-147 (registration)

  Registration of click_by_uid handler in the toolHandlers Map used by the MCP server to route CallToolRequest to handleClickByUid.

    // 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:174-181 (registration)

  Registration of clickByUidTool schema in the allTools array returned by ListToolsRequest.

  // Input
  tools.clickByUidTool,
  tools.hoverByUidTool,
  tools.fillByUidTool,
  tools.dragByUidToUidTool,
  tools.fillFormByUidTool,
  tools.uploadFileByUidTool,

• src/firefox/dom.ts:132-147 (helper)

  Low-level implementation in DomInteractions class: resolves UID to WebElement, waits for visibility, performs click or doubleClick using Selenium actions, waits for event propagation.

  async clickByUid(uid: string, dblClick = false): Promise<void> {
    if (!this.resolveUid) {
      throw new Error('clickByUid: resolveUid callback not set. Ensure snapshot is initialized.');
    }
    const el = await this.resolveUid(uid);
    await this.driver.wait(until.elementIsVisible(el), 5000).catch(() => {});
  
    if (dblClick) {
      await this.driver.actions({ async: true }).doubleClick(el).perform();
    } else {
      await el.click();
    }
  
    // Wait for events to propagate
    await this.waitForEventsAfterAction();
  }