schema.json

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "additionalProperties": false,
  "definitions": {
    "AnotherSubObject": {
      "additionalProperties": false,
      "properties": {
        "b": {
          "type": "boolean"
        }
      },
      "required": ["b"],
      "type": "object"
    },
    "MySubObject": {
      "additionalProperties": false,
      "title": "filled#",
      "type": "object",
      "properties": {
        "a": { "type": "boolean" }
      },
      "required": ["a"]
    }
  },
  "properties": {
    "empty": {
      "title": "empty#"
    },
    "filled": {
      "$ref": "#/definitions/MySubObject",
      "title": "filled"
    },
    "nonTitled": {
      "$ref": "#/definitions/AnotherSubObject"
    }
  },
  "required": ["empty", "filled", "nonTitled"],
  "type": "object"
}