content: {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "properties": {
      "myArray": {
        "contains": {
          "properties": {
            "itemType": {
              "const": "type A"
            }
          }
        },
        "items": {
          "properties": {
            "itemType": {
              "type": "string"
            }
          }
        },
        "maxContains": 1,
        "type": "array"
      }
    }
  }