[
  {
    "namespace": "aboutConfigPrefs",
    "description": "experimental API extension to allow access to about:config preferences",
    "events": [
      {
        "name": "onPrefChange",
        "type": "function",
        "parameters": [
          {
            "name": "name",
            "type": "string",
            "description": "The preference which changed"
          }
        ],
        "extraParameters": [
          {
            "name": "name",
            "type": "string",
            "description": "The preference to monitor"
          }
        ]
      }
    ],
    "functions": [
      {
        "name": "getCheckableGlobalPrefs",
        "type": "function",
        "description": "Lists the global prefs the addon may read",
        "parameters": [],
        "returns": {
          "type": "array",
          "description": "The list of pref names.",
          "items": {
            "type": "string"
          }
        }
      },
      {
        "name": "getPref",
        "type": "function",
        "description": "Get a preference's value",
        "parameters": [
          {
            "name": "name",
            "type": "string",
            "description": "The preference name"
          },
          {
            "name": "defaultValue",
            "type": "boolean",
            "optional": true,
            "description": "Default value to return if the pref is not set"
          }
        ],
        "returns": {
          "choices": [
            { "type": "boolean" },
            { "type": "integer" },
            { "type": "string" }
          ],
          "optional": true,
          "description": "returns the value of a pref."
        }
      }
    ]
  }
]