transfer_started | Tried Docs

Sent when the agent begins transferring a phone call, with the destination and transfer type.

transfer_started tells you the agent is handing a phone call to someone else. It is the first of four transfer events:

Event	Meaning
`transfer_started`	The agent began the transfer
`transfer_bridged`	The destination answered and is connected to the caller
`transfer_cancelled`	The transfer failed or was cancelled
`transfer_ended`	The bridged legs hung up

A successful transfer sends transfer_started, transfer_bridged, then later transfer_ended. A failed one sends transfer_started then transfer_cancelled.

When it fires#

The agent runs a Transfer Call tool (cold, warm or agentic warm transfer). The event fires after the agent finishes speaking and before the destination is dialled. See Transfer call.
An inbound caller waited in the concurrency queue and the number has a fallback_number. The call is cold transferred to that number, which sends transfer_started followed by call_ended with disconnection_reason call_transfer.

Transfer events are sent for phone calls only. Web calls cannot be transferred.

Which settings enable it#

Off by default. Add transfer_started to the agent's webhook_events, or toggle it under Webhook Settings, Events.
URL: the agent's webhook_url, else the workspace URL. {{variable}} placeholders in the agent URL are not filled for transfer events.
Timeout: the workspace timeout, else 10 s. The agent's webhook_timeout_ms does not apply to transfer events.

Payload#

The body has three keys: event, the call object and a transfer object.

{
  "event": "transfer_started",
  "call": {
    "call_id": "call_8c2e5a1f7b3d9e0c4a6f2b18",
    "call_type": "phone_call",
    "agent_id": "agent_5b0e2c7d9a1f4e3b8c6d2a10",
    "agent_version": 2,
    "agent_name": "Bondi Dental Front Desk",
    "call_status": "ongoing",
    "direction": "inbound",
    "from_number": "+61412345678",
    "to_number": "+61291234567",
    "metadata": {},
    "retell_llm_dynamic_variables": { "business_name": "Bondi Dental" },
    "collected_dynamic_variables": {},
    "start_timestamp": 1760675400120,
    "end_timestamp": null,
    "duration_ms": null,
    "transcript": "Agent: Hi, thanks for calling Bondi Dental, this is Ava. How can I help you today?\nUser: I need to talk to the dentist about my bill.\nAgent: Sure, I'll put you through to our practice manager now.",
    "transcript_object": [
      { "role": "agent", "content": "Hi, thanks for calling Bondi Dental, this is Ava. How can I help you today?", "words": [] },
      { "role": "user", "content": "I need to talk to the dentist about my bill.", "words": [] },
      { "role": "agent", "content": "Sure, I'll put you through to our practice manager now.", "words": [] }
    ],
    "transcript_with_tool_calls": [
      { "role": "agent", "content": "Hi, thanks for calling Bondi Dental, this is Ava. How can I help you today?", "ts": 1760675400340 },
      { "role": "user", "content": "I need to talk to the dentist about my bill.", "ts": 1760675405910 },
      { "role": "tool_call_invocation", "tool_call_id": "call_tool_01", "name": "transfer_to_manager", "arguments": "{}", "ts": 1760675406650 },
      { "role": "agent", "content": "Sure, I'll put you through to our practice manager now.", "ts": 1760675406700 },
      { "role": "transfer", "event": "transfer_started", "destination": "+61298765432", "ts": 1760675409210 }
    ],
    "recording_url": null,
    "recording_multi_channel_url": null,
    "public_log_url": "https://api.tried.com.au/public/calls/call_8c2e5a1f7b3d9e0c4a6f2b18/log?exp=1761280209300&sig=1d4a7c0f3b6e9a2d5c8f1b4e7a0d3c6f9b2e5a8d1c4f7b0e3a6d9c2f5b8e1a4d",
    "knowledge_base_retrieved_contents_url": "https://api.tried.com.au/public/calls/call_8c2e5a1f7b3d9e0c4a6f2b18/kb-retrievals?exp=1761280209300&sig=4e7a0d3c6f9b2e5a8d1c4f7b0e3a6d9c2f5b8e1a4d7c0f3b6e9a2d5c8f1b4e7a",
    "transfer_destination": "+61298765432",
    "llm_token_usage": { "values": [1650, 1720], "average": 1685, "num_requests": 2 },
    "disconnection_reason": null,
    "call_analysis": null,
    "latency": {
      "e2e": { "p50": 702, "p90": 702, "p95": 702, "p99": 702, "max": 702, "min": 688, "num": 2, "values": [688, 702] }
    },
    "call_cost": null,
    "batch_call_id": null,
    "contact_id": "contact_6e2a9c1f4b7d0e3a5c8f1b24"
  },
  "transfer": {
    "destination": "+61298765432",
    "transfer_type": "warm_transfer",
    "timestamp": 1760675409210
  }
}

Fields#

The call object is documented on Call object. At this point call_status is ongoing and transfer_destination is set.

Field	Type	Description
`transfer.destination`	string	The number or SIP URI being dialled, after dynamic variables are filled in
`transfer.transfer_type`	string	`cold_transfer`, `warm_transfer` or `agentic_warm_transfer`. Only on `transfer_started`
`transfer.timestamp`	integer	When the transfer started, Unix ms
`call.transfer_destination`	string	Same as `transfer.destination`
`call.transcript_with_tool_calls`	array	Ends with a `{"role": "transfer", "event": "transfer_started"}` entry

How to respond#

Reply 2xx. The body is ignored and cannot stop the transfer. Delivery runs in the background, so the transfer never waits for your server. Failed attempts are retried up to 3 times (1 s, 2 s, 4 s).

Common uses: screen-pop the caller's record for the person about to answer, or start a timer to measure how long transfers take to connect.