Tool call does not get triggered during phone call...
# supportu
undergrowthseer
03/25/2025, 9:32 AMcallId - d6fd59e6-a06a-4995-b4a2-443fa67c76d8
response expected - Statement "you are awesome" or at least a ping to my endpoint
response actual - Just generic response as the agent "figures" out what i was asking
v
Vapi Support Bot
03/25/2025, 9:34 AM2. **Verify JSON Response Format**: Make sure your endpoint returns the correct JSON format that VAPI expects:
Copy code
json
{
"results" : [ {
"toolCallId":"1. message.toolCalls[].id",
"result":"Whatever you want to send back to the tool"
}
]
}Vapi Support Bot
03/25/2025, 9:34 AMHi there! 👋
I see you're having an issue with tool calls not triggering during phone calls, while they work fine with web calls. Unfortunately, I can't analyze your specific call ID in detail, but I can definitely help with information about this known issue and some troubleshooting steps!
According to [Discord discussions](https://discord.com/channels/1211482211119796234/1211483291191083018/threads/1334666797932089405), this exact issue has been reported by other users - tool calls working in web calls but not in phone calls. There are several potential causes for this:
## Known Issues
1. **Client-side vs. Server-side Tool Calls**: Web calls use WebRTC data channels for client-side tool calls, while phone calls handle tools differently. According to [Discord information](https://discord.com/channels/1211482211119796234/1211483291191083018/threads/1342336047589359618), this fundamental difference can affect tool call triggering.
2. **Model Behavior Issues**: In approximately 20% of cases, the model might speak the internal VAPI tool call code instead of executing it, particularly with the
transfer_callassistantOptions Copy code
javascript
tools: [{
"type": "function",
"function": {
"name": "your_tool_name",
"description": "Description of your tool",
"strict": true,
"parameters": { ... }
},
"async": false
}]u
undergrowthseer
03/25/2025, 10:21 AM@User I am developing on local using ngrok for reverse proxy. I do have "strict": false on mine, is that an issue? The main thing that is noticeable on the logs (both app and ngrok) is that there are no attempts to even try to reach the endpoint (server.url) compared to the web ui call where you'll see that there is an attempt to do a POST request to the endpoint.
a
amurgio
03/25/2025, 3:46 PMall my tool calls stopped working in the past couple hours
u
undergrowthseer
03/26/2025, 12:32 AMfor phone calls? did it ever affect web ui calls for you? has it come back online on your end?
s
Shubham Bajaj
03/26/2025, 2:26 PM@amurgio please create a new support ticket for your issue
k
Kyle Brunker
03/26/2025, 2:27 PMYou need to change your model from GPT 3.5 Turbo to either GPT 4.0 or GPT 4.0 mini and also work on prompting which is a pure prompting and model problem not related to VAPI. So yeah rework on your prompt and even if after rework doesn't works please change your prompt to GPT 4 or GPT 4.0 mini for prompting help you can checkout our VAPI prompting guide doc .
u
undergrowthseer
03/27/2025, 1:31 AMCan you explain what's the difference why it works on WebUI and not a direct phone call? I have the same prompt, I did the same response and the prompt is very simple ask the recipient a question and if he/she says yes you reach out to the tool.
EDIT:
- I've tried to change to gpt-4o and gpt-4o-mini as well
- I've also followed your guidelines from the link you provided
- I've tested on both, Web UI and direct to Phone and the web UI without fail will send a request to my webhook endpoint, but the phone call does not attempt to try to send a request at all.
callid of the phone call cb64dc49-2a30-4da3-9923-bd5c27b88373
callid of the web call 43bb9a2c-584c-4451-84b1-1bc6ad19741c
undergrowthseer
03/27/2025, 4:02 AM@tejas
t
tejas
03/27/2025, 4:17 AMhm i actually see that the server webhook request succeeds on phone call, but fails with a 500 on the web call, meaning your server did not respond for the web call
u
undergrowthseer
03/27/2025, 4:35 AM@User Correct, but the issue is the other call does not even try to request
t
tejas
03/27/2025, 5:17 AMthats the thing i do see successful requests for that call
Server Message Successful. (https://ff9a-219-76-18-202.ngrok-free.app/api/callbacks/vapi). Response: {"result": "Your call has ended and saved."}u
undergrowthseer
03/27/2025, 9:45 AMcorrect, that's after the call has been hung up. at the end-of-call report, or before that happens.
undergrowthseer
04/01/2025, 3:04 AM@tejas @Shubham Bajaj any updates on this? can you point me to anyone i can speak with regarding this?
k
Kyle Brunker
04/01/2025, 10:07 PMHey! To help track down this issue, could you share:
- The call ID
- What response you expected to get
- What response you actually got instead
This would really help us figure out what went wrong!
Kyle Brunker
04/01/2025, 10:08 PMI was under the impression that your ticket has been resolved. But please share the following information, and I'll help you with the solution.