Firefox OS app submission: "The webapp manifest is not valid JSON."

I want to upload my app to the Firefox marketplace. But when uploading my app, a validation error shows:

The webapp manifest is not valid JSON.

I am using this manifest code:

{
  "name": "Web browser",
  "description": "A simple web browser.",
  "launch_path": "/index.html",
  "type": "privileged",
  "icons": {
    "512": "/img/firefox512.png",
    "128": "/img/firefox128.png"
  },
  "developer": {
    "name": "Gourab"

  },

  "permissions": {
    "browser": {
    "description": "Required to use browser API.",
    }
  }

}

But if I remove the description part of Browser permission, then the error message comes with:

Error: The 'browser' node of the Web App Manifest expects a description element, which was not found.

You can find more information at https://developer.mozilla.org/docs/Web/Apps/Manifest

Node: root > permissions > browser
manifest.webapp

Can anyone give me a solution of this problem?

There is extra , in this line

"description": "Required to use browser API.", // <--- remove this , 

Remove that and you are ready to fly

Valid

{
  "name": "Web browser",
  "description": "A simple web browser.",
  "launch_path": "/index.html",
  "type": "privileged",
  "icons": {
    "512": "/img/firefox512.png",
    "128": "/img/firefox128.png"
  },
  "developer": {
    "name": "Gourab"

  },

  "permissions": {
    "browser": {
    "description": "Required to use browser API."
    }
  }

}