Firefox MCP Server

Instructions

Implementation Reference

• index-multi-debug.js:612-658 (handler)

  Main handler function for 'create_tab' tool. Creates a new browser context and page (tab), initializes debug buffers, optionally sets up monitoring, navigates to the specified URL, stores the page, and sets it as active if none exists.

  async createTab(args) {
    this.ensureBrowserRunning();
    const { tabId, url = 'about:blank', contextId, enableMonitoring = true } = args;
    
    if (this.pages.has(tabId)) {
      throw new Error(`Tab with ID '${tabId}' already exists`);
    }
  
    // Create or reuse context
    const effectiveContextId = contextId || `context-${tabId}`;
    let context;
    
    if (this.contexts.has(effectiveContextId)) {
      context = this.contexts.get(effectiveContextId);
    } else {
      context = await this.browser.newContext({
        storageState: undefined // Start with clean state
      });
      this.contexts.set(effectiveContextId, context);
    }
  
    // Create new page in the context
    const page = await context.newPage();
    
    // Initialize debug buffers
    this.initDebugBuffers(tabId);
    
    // Setup monitoring if enabled
    if (enableMonitoring) {
      await this.setupPageMonitoring(page, tabId);
    }
    
    await page.goto(url);
    this.pages.set(tabId, page);
    
    // Set as active tab if no active tab exists
    if (!this.activeTabId) {
      this.activeTabId = tabId;
    }
  
    return {
      content: [{
        type: 'text',
        text: `Tab '${tabId}' created with debugging ${enableMonitoring ? 'enabled' : 'disabled'}. URL: ${url}. Context: ${effectiveContextId}`
      }]
    };
  }

• index-multi-debug.js:59-70 (schema)

  Input schema definition for the 'create_tab' tool, specifying parameters tabId (required), url, contextId, enableMonitoring.

  name: 'create_tab',
  description: 'Create a new tab with isolated session and debugging',
  inputSchema: {
    type: 'object',
    properties: {
      tabId: { type: 'string' },
      url: { type: 'string', default: 'about:blank' },
      contextId: { type: 'string' },
      enableMonitoring: { type: 'boolean', default: true }
    },
    required: ['tabId']
  }

• index-multi-debug.js:399-400 (registration)

  Registration/dispatch in the CallToolRequestSchema handler switch statement, calling the createTab method.

  case 'create_tab':
    return await this.createTab(args);

• index-multi-debug.js:58-71 (registration)

  Tool registration object in the ListToolsRequestSchema response tools array.

  {
    name: 'create_tab',
    description: 'Create a new tab with isolated session and debugging',
    inputSchema: {
      type: 'object',
      properties: {
        tabId: { type: 'string' },
        url: { type: 'string', default: 'about:blank' },
        contextId: { type: 'string' },
        enableMonitoring: { type: 'boolean', default: true }
      },
      required: ['tabId']
    }
  },