json.invalid

{
  "topic": "unknown/unknown/things/twin/errors",
  "headers": {},
  "path": "/",
  "value": {
    "status": 400,
    "error": "json.invalid",
    "message": "Could not read 'foo'",
    "description": "Check if the JSON was valid (e.g. on http://jsonlint.com) and if it was in required format."
  },
  "status": 400
}