Ligth control with mqtt and json misunderstanding

Hardware
1

Hi,

I am having some trouble getting a Shelly vintage light to work in my configuration.yaml, i can get the device to switch nicely through home assistant -> interactions -> mqtt tile -> configure using a JSON payload of:

{"turn": "off"}
or 
{"turn": "on"}

Currently, I have entered the code below into my configuration.yaml with little luck.
I cant see how the home assistant would know what JSON string to send to the device with the code below, I suspect I need to use payload_on: or command_on to send the JSON but I can’t find it in the doc’s

light:
  - platform: mqtt
    name: "Shelly sidelight"
    schema: json
    state_topic: "shellies/ShellyVintage-D0FE8B/light/0/status"
    command_topic: "shellies/ShellyVintage-D0FE8B/light/0/set"
    brightness: true

P.S am using the Shelly discovery script but it doesn’t show up the bulbs as I think there is a bug, so this is why I’m using yaml.

home assistant -> interactions -> mqtt tile -> configure using

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