v1/v2 vs v3 event payload data formats?

Hello,

We have a completely custom integration where we post JSON data to the /track API to create events and trigger customer notification emails, etc.

We’re now faced with migrating to the new APIs. The documentation around the migration from v1/v2 to the new APIs is ver clear on the new endpoints such as /api/events and new functionality etc.

However what’s not so clear to me is any change between the data format of the original API payloads vs new API payloads?

The Track API reference (https://developers.klaviyo.com/en/v1-2/docs/track-api-reference#back-end-tracking-events-server-side) refers to special fields such as $event_id, $value, $email, $first_name etc. However I cannot find any reference to these in the new documentation. For example the documentation for Create Event (https://developers.klaviyo.com/en/reference/create_event) gives the example payload JSON below:
 

{
  "data": {
    "type": "event",
    "attributes": {
      "properties": {
        "newKey": "New Value"
      },
      "time": "2022-11-08T00:00:00",
      "value": 9.99,
      "value_currency": "USD",
      "metric": {
        "data": {
          "type": "metric",
          "attributes": {
            "name": "Viewed Product"
          }
        }
      },
      "profile": {
        "data": {
          "type": "profile",
          "id": "01GDDKASAP8TKDDA2GRZDSVP4H",
          "attributes": {
            "email": "sarah.mason@klaviyo-demo.com",
            "phone_number": "+15005550006",
            "external_id": "63f64a2b-c6bf-40c7-b81f-bed08162edbe",
            "_kx": "J8fjcn003Wy6b-3ILNlOyZXabW6dcFwTyeuxrowMers%3D.McN66",
            "first_name": "Sarah",
            "last_name": "Mason",
            "organization": "Example Corporation",
            "title": "Regional Manager",
            "image": "https://images.pexels.com/photos/3760854/pexels-photo-3760854.jpeg",
            "location": {
              "address1": "89 E 42nd St",
              "address2": "1st floor",
              "city": "New York",
              "country": "United States",
              "region": "NY",
              "zip": "10017",
              "timezone": "America/New_York",
              "ip": "127.0.0.1"
            },
            "properties": {
              "newKey": "New Value"
            }
          },
          "meta": {
            "patch_properties": {
              "append": {
                "newKey": "New Value"
              },
              "unappend": {
                "newKey": "New Value"
              },
              "unset": "skus"
            }
          }
        }
      }
    }
  }
}

In this, there is no $event_id field, no $value or $email etc…. so is the data format for create event payloads completely different from event payloads using the old /track API?

Can anybody point me to the documentation/specification for event payloads to /api/events, or something that explains the differences between old and new?

Many thanks in advance, 

Mat