How to define Heroku scheduler job in app.json?

I'm not sure if it's even possible. According to the docs, add-on options can be specified in app.json: https://devcenter.heroku.com/articles/app-json-schema#addons

I tried the following json, and it provisions the scheduler add-on, but without any jobs defined.

"addons": [
  {
    "plan": "scheduler",
    "options": {
      "command": "my command",
      "dyno-size": "Free",
      "every": 10,
      "at": 0
    }
  }
]