Shell Command passing values to curl in automation

I am using shell commands to successfully trigger IFTTT applets from Home Assistant automations.

I can successfully call both of these shell commands from my automations:

shell_command:
    curl_ifttt_no_data: "curl -X POST https://maker.ifttt.com/trigger/{{ event }}/with/key/my_secret_ifttt_key"
    curl_ifttt_data: "curl -X POST -d '{\"value1\":\"{{ value1 }}\",\"value2\":\"{{ value2 }}\",\"value3\":\"{{ value3 }}\"}' https://maker.ifttt.com/trigger/{{ event }}/with/key/my_secret_ifttt_key"

The second one is supposed to pass on data in the form of three values.
My automation’s action looks like this:

service: shell_command.curl_ifttt_data
data:
  event: balcony_door
  value1: 1
  value2: 2
  value3: 3

The action runs the shell command just fine and the IFTTT applet gets triggered, however the values do not arrive at the IFTTT applet.

Has anyone had a similar problem and found a solution to it? Thanks for the help!