Is there any documentation to find the structure of end of call report, I dont seem to find any. For example I want to know if customer field is a direct child of message or not.

Hi saketh_1201, Yes, the structure of end-of-call report is documented under Server events. For example:

{
  "message": {
    "type": "end-of-call-report",
    "endedReason": "hangup",
    "call": { /* Call Object */ },
    "artifact": {
      "recording": { /* Recording object with URLs */ },
      "transcript": "AI: How can I help? User: What's the weather? ...",
      "messages": [
        { "role": "assistant", "message": "How can I help?" },
        { "role": "user", "message": "What's the weather?" }
      ]
    }
  }
}

Please refer (see End of Call Report + the common metadata at the top). You can also confirm the exact structure by making a quick test call and logging the payload. Thanks