To detect voicemails and leave a custom message in Vapi, add this configuration to your workflow:

json
{
  ...yourExistingSettings,
  "voicemailDetection": {
    "provider": "twilio",
    "voicemailDetectionTypes": ["machine_start", "machine_end_beep", "unknown"],
    "enabled": true,
    "machineDetectionTimeout": 15
  },
  "model": {
    "tools": [{ "type": "voicemail" }]
  },
  "voicemailMessage": "This is the custom message I want to leave on voicemail."
}

This combines both Twilio's detection and Vapi's built-in tool for better accuracy, while the

voicemailMessage

parameter specifies your custom message. Source: - [Vapi Documentation](https://docs.vapi.ai/phone-calling/voice-mail-detection)