[
  {
    "namespace": "manifest",
    "types": [
      {
        "$extend": "WebExtensionManifest",
        "properties": {
          "devtools_page": {
            "$ref": "ExtensionURL",
            "optional": true
          }
        }
      },
      {
        "$extend": "OptionalPermission",
        "choices": [
          {
            "type": "string",
            "enum": ["devtools"]
          }
        ]
      }
    ]
  },
  {
    "namespace": "devtools",
    "permissions": ["manifest:devtools_page"],
    "allowedContexts": ["devtools", "devtools_only"],
    "defaultContexts": ["devtools", "devtools_only"]
  }
]