The HA commands:

rest_command:
  turn_off_mm_screen:
    url: http://IP:8080/api/monitor/off
  turn_on_mm_screen:
    url: http://IP:8080/api/monitor/on
  dim_mm_screen:
    url: http://IP:8080/api/brightness/75
  undim_mm_screen:
    url: http://IP:8080/api/brightness/100

One of the automations (at night)

- id: '1557033756115'
  alias: Turn on bathroom light at night
  trigger:
  - entity_id: binary_sensor.bathroom_movement
    from: 'off'
    platform: state
    to: 'on'
  condition:
  - after: '23:00'
    before: '7:59'
    condition: time
  - condition: state
    entity_id: light.spejl
    state: 'off'
  action:
  - data:
      brightness_pct: 10
      entity_id: light.spejl
    service: light.turn_on
  - data: {}
    service: rest_command.turn_on_mm_screen
  - data: {}
    service: rest_command.undim_mm_screen

Next step would be to modify rest_command so that I don’t have one for each action, but send a payload that is modified to the command that I want.