{
  "$schema": "http://json-schema.org/draft-04/schema#",
  "description": "GET notification return schema - for sms notifications",
  "type" : "object",
  "properties": {
    "notifications": {
      "type": "array",
      "items": {
        "oneOf": [
          {"$ref": "sms_notification.json"},
          {"$ref": "email_notification.json"}
        ]
      }
    },
    "links": {
      "type": "object",
      "properties" : {
        "last": {
          "type" : "string"
        },
        "next" : {
          "type" : "string"
        },
        "prev" : {
          "type" : "string"
        }
      }
    },
    "page_size": {"type": "number"},
    "total": {"type": "number"}
  },
  "additionalProperties": false,
  "required": [
    "notifications", "links", "page_size", "total"
  ]
}

{
  "$schema": "http://json-schema.org/draft-04/schema#",
  "description": "GET notification return schema - for sms notifications",
  "type" : "object",
  "properties": {
    "notifications": {
      "type": "array",
      "items": {
        "oneOf": [
          {"$ref": "sms_notification.json"},
          {"$ref": "email_notification.json"}
        ]
      }
    },
    "links": {
      "type": "object",
      "properties" : {
        "prev" : {
          "type" : "string"
        },
        "next" : {
          "type" : "string"
        },
        "last": {
          "type" : "string"
        }
      },
      "additionalProperties": false
    },
    "page_size": {"type": "number"},
    "total": {"type": "number"}
  },
  "additionalProperties": false,
  "required": [
    "notifications", "links", "page_size", "total"
  ]
}

Add additionalProperties to links object
Add additionalProperties to links object
