I changed nothing, it worked since end of Sept. 2025. Now all of a sudden, the assistant halt after sending the SMS (successfully) and waits for user utterance. If no utterance call hangs up due to idling. CALLIDs: 019acb6c-7cde-744a-a478-3307a11f77a9 019acb68-0c1f-7bb7-b186-ee62be0148e8 019acb61-8779-711f-a335-e249a3485b22

Suggestion: Check your assistant's idle message configuration to ensure it prompts the user after the SMS tool completes. For example, add or adjust a

customer.speech.timeout

hook like this:

json
{
  "hooks": [{
    "on": "customer.speech.timeout",
    "options": { "timeoutSeconds": 10, "triggerMaxCount": 3, "triggerResetMode": "onUserSpeech" },
    "do": [{ "type": "say", "exact": "Are you still there?" }]
  }]
}

This will re-engage users if they don't respond after the SMS is sent. See the [Idle Messages documentation](https://docs.vapi.ai/assistants/idle-messages) for more details. Source: - [Idle messages](https://docs.vapi.ai/assistants/idle-messages)

I found out It is not just SMS tool but existing Booking tool - in existing Vapi agent - all untouched and in production since End of Sept. Now since this week all agents have this same problem ...the tool executes and completes , but Vapi requires user utterance to progress to next step - it worked without asking the user for any utterance since 2,5 months.. Very strange is that when testing the agent with chat 💭 it works perfectly normal as before - only when I call it via phone this is a new bug. It was 100% some VAPI change in the backend and apparently after 21st of November because until then no complaints from any client. But now all our agents do this.. drives me crazy and my clients , too. 😭 Other tool calls prior in the callflow / prompt still work like before. It is just these 2 tool calls - booking and SMS - close at the end of the prompt.

You'll want to update your assistant's instructions so they explicitly define how to behave after the SMS tool completes. The key is to prevent the assistant from reading the technical success message aloud and to force it to continue with the normal dialogue flow. Here's the corrected structure you should add to your system prompt:

14. Falls auch eine SMS vom Nutzer gewünscht war, sende die Terminbestätigung auch per SMS an die Rufnummer mit deiner "send_sms_tool" Function.
    - WICHTIG: Sage NICHT die technische Erfolgsmeldung dem Nutzer!
    - Nach erfolgreichem SMS-Versand direkt mit Schritt 15 fortfahren.

15. Nach erfolgreichem SMS-Versand sage: "Großartig, Herr/Frau {{name}}! Der Termin ist erfolgreich gebucht. Sie erhalten gleich eine SMS-Bestätigung."

16. Frage dann: "Kann ich noch etwas für Sie tun?"
    - Falls nein: Verabschiede dich höflich und nutze die "endCall" Function.

Adding these explicit steps ensures the assistant moves smoothly from tool execution back into the expected conversational flow instead of pausing and waiting for additional user input.

Kyle, thanks a lot for trying to help. Much appreciated! Sadly your solution did not work! (I believe we have a misunderstanding: The assistant never was "reading out aloud" the success message. I have a different issue. Kindly request you to look into this in detail, once more as it MUST be related to some very recent (around 21-29th Nov) backend change / update at VAPI. Let me re-summarize the issue: I'm experiencing an issue that started after November 21st, 2025. ISSUE: - My assistant goes silent after a tool call succesfully completes (bookappt, send sms) in VOICE mode - The same flow works perfectly in CHAT mode - The assistant waits for user input before speaking the confirmation line in the next prompt step after book and sms - After user speaks, the assistant finally delivers the queued message CONFIGURATION: - Organization: [a61bf531-ae29-4a36-970f-e7344054d308] - Assistant ID: [20601811-5e35-4c06-8057-caaa02341cf4] - Update Channel: Weekly (since September 2025) - Call ID with issue: [019acb6c-7cde-744a-a478-3307a11f77a9 019acb68-0c1f-7bb7-b186-ee62be0148e8, 019adf9c-14ec-7ccb-b141-bb9f8256709b] WHAT I'VE TRIED: - [I have tried working on the tool response in make.com, but tbh that is not the solution as it works fine in chatmode] - I have changed the prompt, own ideas and your recommendation - did not work at all TIMELINE: - Worked perfectly before November 21st, 2025 - Broken after November 21st, 2025 - No configuration changes on my end This appears to be related to voice pipeline handling after tool calls, as the exact same configuration works in chat mode. Could you please investigate and advise? In chat it progresses naturally to next step in flow after tool execution. So it can´t be some change with regards to tool response, it must be a Vapi side change Please can we have a call to look into this? Can you please kindly do further analysis. I am not the only one with this issue, as I know from speaking with other Vapi users.

Thanks for the detailed breakdown — this helps a lot. We've identified that your assistant is likely waiting for a completion signal after the SMS tool executes in voice mode, even though chat mode continues normally. To fix this, you can explicitly provide that completion signal by adding a

role: "system"

request-complete message to your SMS tool configuration. Please update your

send_sms_tool

message block as follows:

json
{
  "type": "sms",
  "messages": [
    {
      "type": "request-start",
      "content": " ",
      "blocking": false
    },
    {
      "type": "request-complete",
      "role": "system",
      "content": "SMS was sent successfully. Confirm this to the user and ask if they need anything else."
    }
  ]
  // ... rest of config
}

This explicitly tells the voice pipeline that the tool action is finished and that the assistant should continue speaking without waiting for user utterance. Let me know once you’ve tried this, or if you'd like me to help modify the full config for your assistant.

Thank you Kyle! It didn´t work. Apparently VAPI does not allow the modification of the standard Vapi provided SMS Tool via API Reference Tool ? I use Vapi´s preconfigured SMS function "SEND TEXT", that you offer in the Dashboard unter /Tools/create tool/send text. When using the API Ref Tool to update the tool function as you said, it returns an error all the time, as soon as I configure a start or end message for the tool. : { "message": [ "property type should not exist" ], "error": "Bad Request", "statusCode": 400 } --- Any ideas how to get this working? (Of course I can configure start and end message in the dashboard, tools, smstool and configure it, but then i can not set the role to System, only assistant messages are allowed. Can you help? SMS Tool ID to work on I can share in private chat, to avoid fraudsters to get it.

Hi there, Thanks for the update — we're glad to hear you were able to find a workaround for now. We’ll pass this feedback along to our engineering team so they’re aware of the behavior change you encountered. Since you’ve moved forward with an alternative solution, we’ll go ahead and close this ticket for now. If anything changes or you’d like us to revisit this in the future, just reply here and we’ll be happy to reopen it. Thanks again for your patience and for flagging this. Best, Vapi Support