Examine source code of CountMyTabs

{
  "name": "Tab Counter",
  "version": "1.0.0",
  "description": "Counts the Tabs",
  "manifest_version": 2,
  "author": "Shourya Wadhwa",
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Tab Counter",
    "default_icon": {
      "512": "icons/tab.png"
    }
  },
  "permissions": [
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c1a14861-754e-4594-84d0-86ad500410fa}"
    }
  }
}