Firefox MCP Server

Instructions

Implementation Reference

• index-multi-debug.js:1327-1339 (handler)

  The core handler function for the 'get_current_url' tool. It ensures the browser is running, gets the page for the specified or active tab, retrieves the current URL using page.url(), and returns it formatted in MCP response.

  async getCurrentUrl(args = {}) {
    this.ensureBrowserRunning();
    const { tabId } = args;
    const page = this.getPage(tabId);
    const url = page.url();
    
    return {
      content: [{
        type: 'text',
        text: `Current URL in tab '${tabId || this.activeTabId}': ${url}`
      }]
    };
  }

• index-multi-debug.js:228-235 (schema)

  The tool schema definition in the listTools response, specifying name, description, and input schema (optional tabId string).

  {
    name: 'get_current_url',
    description: 'Get current page URL',
    inputSchema: {
      type: 'object',
      properties: { tabId: { type: 'string' } }
    }
  },

• index-multi-debug.js:429-430 (registration)

  Registration in the CallToolRequestSchema handler switch statement, dispatching calls to the getCurrentUrl method.

  case 'get_current_url':
    return await this.getCurrentUrl(args);

• index-multi-debug.js:1021-1033 (helper)

  Helper method used by getCurrentUrl to retrieve the Playwright Page object for the given tabId or the active tab.

  getPage(tabId) {
    if (tabId) {
      if (!this.pages.has(tabId)) {
        throw new Error(`Tab '${tabId}' not found`);
      }
      return this.pages.get(tabId);
    } else {
      if (!this.activeTabId || !this.pages.has(this.activeTabId)) {
        throw new Error('No active tab. Use create_tab or set_active_tab first.');
      }
      return this.pages.get(this.activeTabId);
    }
  }

• index-multi-debug.js:1400-1405 (helper)

  Helper method called by getCurrentUrl to ensure the browser instance is launched before accessing pages.

  ensureBrowserRunning() {
    if (!this.browser) {
      throw new Error('Firefox browser is not running. Please launch it first using the launch_firefox_multi tool.');
    }
  }