MQTT discovery ERROR "extra keys not allowed @ data['brightness']"

Hi,
can anyone point me to the right direction why I am getting that error message when trying to get an light configured via mqtt discovery? I ran out of ideas and I’m apparently overseeing sth. Tested with HA 0.77 to 0.78.1

{
  "name":"test99",
  "cmd_t":"light/test99/cmd",
  "stat_t":"light/test99/state",
  "uniq_id":"light.test99",
  "avty_t":"esp99/lwt",
  "pl_avail":"online",
  "pl_not_avail":"offline",
      "ret":true,
      "brightness":true,
      "rgb":true,
      "color_temp":true,
      "hs":true,
      "effect":true,
      "effect_list":[
        "static",
        "breath",
        "fade",
        "strobe",
        "multi strobe",
        "comet",
        "fire"
      ],
      "device":{
        "sw_version":20190215,
        "manufacturer":"michbaeck",
        "model":"PLATFORMIO_D1_MINI",
        "name":"esp99",
        "connections":[
          ["mac","CC:50:E3:08:08:75"]
        ],
        "identifiers":[
          "526453",
          "CC50E3080875"
        ]
      }
    }

meeh…nevermind, got it.

Forgot to add “schema”:“json” which is explained but not listed in the docs. Then after deleting and republishing it’s working now