Mqtt light with json


i have a light , and i can control it via mqtt ( through node red )

inside configuration.yaml i have :

# Example configuration.yaml entry 
  - light:
      name: "mqtt_json_light_eettafeltemplateversie"
      schema: template
      command_topic: "peha/home/rgb1/set"
      command_on_template:  "{ "brightness": 22, "mod": 0, "evt": 0, "cha": 0, "transition": 20, "state": "ON" }"
      command_off_template: "off"   

if you manipulate the Homeassistant light button ans set it on or set a value via de GUI ,
i want to recieve a payload in 1 JSON format instead of 2 separate mqtt topics .
how can i achieve this , that a user send this json to my node-red ?

{ “brightness”: 22, “mod”: 0, “evt”: 0, “cha”: 0, “transition”: 20, “state”: “ON” }

i asked chatGPT , but the solution did not work
i read the manuals , but maybe i dont understand some important details.
please who can point me in the good direction , so that my payload is json instead of string