exotic-emerald
exotic-emerald•4h ago

Urgent: transferCall and handoff Tools Failing to Locate Destination Assistant

Hey team, I’ve added the default options available in the dropdown, but I believe there’s a broader issue with the transferCall tool — it’s currently not working. During both test and production runs, I keep getting this error: assistantDestination ‘Not Found’ even though the destination assistant exists. I also tried using the handoff tool instead, but the functionality didn’t work either — the system prompt changed, but the voice settings of the destination assistant were not applied (the destination assistant is in Spanish). Our main goal is simply to transfer calls to a language-based assistant (English or Spanish). We can’t use squad, since there’s no outbound campaign endpoint available — though I’ve tested that setup as well. Problem recap: • Handoff Tool: Switches only the system prompt; does not update the voice settings for the Spanish destination assistant. • TransferCall Tool: Returns this error even though the destination assistant exists: Error: call.start.error-get-assistant Invalid Destination. Assistant "YUB_English" Not Found. {"error":"Bad Request","statusCode":400} Please treat this as urgent — we’re currently blocked on multi-language call transfers. Organization ID: 8fcae760-23cb-4857-a7bc-32a982810e88 Assistants: • YUB_Router • YUB_Spanish • YUB_English
1 Reply
Vapi Support Bot
Vapi Support Bot•4h ago
To resolve the "assistantDestination 'Not Found'" error with the transferCall tool, ensure your tool's parameters include the required destination property with the correct assistant ID or phone number. Here's a sample configuration for your tool's parameters section: 
"parameters": {
  "type": "object",
  "properties": {
    "destination": {
      "type": "string",
      "enum": ["YUB_English"], // Use the exact assistant ID or phone number
      "description": "The destination assistant ID or number to transfer the call to."
    }
  },
  "required": ["destination"]
}
"parameters": {
  "type": "object",
  "properties": {
    "destination": {
      "type": "string",
      "enum": ["YUB_English"], // Use the exact assistant ID or phone number
      "description": "The destination assistant ID or number to transfer the call to."
    }
  },
  "required": ["destination"]
}
Update your tool configuration with this snippet, replacing "YUB_English" with the correct assistant ID if needed. This should resolve the destination not found error and allow call transfers to your language-based assistants. Sources: - Vapi documentation: call forwarding - Vapi Discord Support Example
⤵️ Mention @Vapi Support Bot for follow-ups 🐥

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