Hi VAPI team, I'm encountering an issue where the transferCall tool does not work correctly when the call is started using a squad that includes multiple assistants. Problem Description When I initiate a call with a squad that contains more than one assistant, the transferCall tool (which is configured to call our server for routing) stops functioning as expected. It appears that VAPI gets confused between: An assistant-to-assistant transfer (via the squad), and A transferCall tool execution that should be handled by our backend via a custom URL. Current Behavior (with multiple assistants in squad) When more than one assistant is included in the squad, the transferCall tool that should trigger our backend stops working altogether. It seems like VAPI is incorrectly interpreting this as a squad member handoff or internal assistant transfer, rather than a tool-based call. Example Payload Used for assistant-request

typescipt
{
  "squad": {
    "members": [
      {
        "assistantId": "f4415bca-e04f-427a-a15f-5833ff3c9002",
        "assistantOverrides": {
          "variableValues": {
            "quote_assistant": "Will QA 592dd5-021774"
          }
        },
        "assistantDestinations": [
          {
            "type": "assistant",
            "assistantName": "Will QA 592dd5-021774",
            "message": "",
            "description": "Transfer the user to the quote assistant Will QA 592dd5-021774."
          }
        ]
      },
      {
        "assistantId": "f74dcf3d-d2e8-4fa5-8712-7e41b47b42fe"
      }
    ]
  }
}

Remove the

"phone-call-control"

event from assistants, clearly separate internal

assistantDestinations

from backend

transferCall

routes, and explicitly trigger

transferCall

in the assistant's output to ensure your backend is called correctly..

The

phone-call-control

event is not selected in the assistant. The assistantDestinations and transferCall routes are clearly separated: assistantDestinations is assigned at the start of the phone call upon receiving the assistant-request event, while transferCall is a separate tool that triggers a call to my server.

Even with phone-call-control disabled and clear separation of assistantDestinations and transferCall, Vapi prioritizes internal assistant transfers in squads, so to ensure backend transferCall execution, use single-assistant calls for tool-based routing and reserve squads only for assistant-to-assistant handoffs..