### Answer Based on the symptoms you're describing, where the agent is verbalizing the transfer action instead of executing it (showing

<call:default_api:transfer_call_variabel{...} />

) , this appears to be a function calling execution issue rather than a warm transfer configuration problem. [(1) ]() To properly configure the Transfer Call tool, you need to: 1. Add the Transfer Call Tool - Click "+ Add" in the tools section and select "Transfer Call" from the dropdown menu 2. Set the transfer destination to either: - A number in e.164 format - A SIP URI in the format

sip:username@domain

- A dynamic variable that gets substituted at runtime 3. Configure the transfer type - Choose between cold transfer or warm transfer 4. Update your prompt to include specific instructions about when to use the transfer_call tool, such as: "If the user is angry or frustrated, use the transfer_call tool to transfer the conversation to a human agent." The issue you're experiencing suggests the LLM is generating the function call syntax but the system isn't executing it. This could be related to: - Improper tool configuration in your agent setup - The function not being properly registered - Permissions issues with the transfer destination number For warm transfers specifically, you can configure additional settings like on-hold music, human detection, whisper messages, and three-way handoff messages. I recommend checking your agent configuration to ensure the transfer_call function is properly set up with the correct parameters and that your prompt clearly instructs when to invoke it.

​ To learn more, see the sources I considered: [[1] Transfer call](https://docs.retellai.com/build/single-multi-prompt/transfer-call) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.