Hey Vapi Team, A fellow waterloo Alum and and co-founder of Keyflow (https://keyflow.space) here. We are trying to build an integration for Vapi in our AI workflow automation platform so users can build voice assistants on Vapi and connect it to other system of records like CRMs, email inbox, etc. We constantly keep getting this error when Vapi sends us a webhook back. We have an

https://

url and yet it asks us to send a valid

https://

or

wss://

url. Can someone please assist us on what is going on here. Not really sure what the issue is.

Status code: 400 Body: { "message": [
"assistantOverrides.server.url must be al valid URL. Hot tip, the protocol should be https:// or wss://, but found https://keyflow-
backend-62hevvkvea-
uc.a.run.app/api/trigger/vapi/webhook" ],
"error": "Bad Request", "statusCode": 400 }.

https://cdn.discordapp.com/attachments/1350125273806536745/1350125274125176842/Screenshot_2025-03-14_at_10.27.11_AM.png?ex=67d599a5&is=67d44825&hm=7e68b86e4c44abc7e530a1bc2946511895e79c58e97b0bf049f339a56a4ff843&

Hi there, fellow Waterloo alum! 👋 I can see what's happening with your webhook URL. Looking at the error message, I noticed your URL appears to have line breaks in it:

https://keyflow-
backend-62hevvkvea-
uc.a.run.app/api/trigger/vapi/webhook

This is likely causing the validation error. The URL needs to be a single continuous string without any breaks or special characters. Try updating your webhook URL to:

https://keyflow-backend-62hevvkvea-uc.a.run.app/api/trigger/vapi/webhook

When configuring webhooks in Vapi, remember: 1. URLs must be publicly accessible 2. Only

https://

or

wss://

protocols are accepted 3. The server URL follows a specific order of precedence:

assistant.server.url

→

phoneNumber.serverUrl

→

org.serverUrl

If you're still experiencing issues after fixing the URL format, you might want to try manually testing your webhook endpoint with a tool like Postman or cURL to verify it's accessible and responding correctly. Let me know if this helps resolve your issue! Sources: - [Accepted protocols and URL formats for configuring webhooks in Vapi](https://docs.vapi.ai/server-url) - [Common causes of a 400 Bad Request error when Vapi sends a webhook](https://discord.com/channels/1211482211119796234/1211483291191083018/threads/1343699958874787896) - [How to troubleshoot and resolve URL validation errors for Vapi webhooks](https://discord.com/channels/1211482211119796234/1211483291191083018/threads/1336345690393149452)

Any more updates?

Hey! To help track down this issue, could you share: - The call ID This would really help us figure out what went wrong!

@trillhouse An reminder message to continue this thread if we didn't receive any further response then eventually we have to mark this thread to be closed. So please reply back with a required call ID.

@User Sure, let me find the call id

@trillhouse I can see there's an issue with your VAPI API call. Looking at the error message and request data, I've identified the problem. The error is occurring because there's a leading space in the

assistantOverrides.server.url

field. In your request body, the URL is:

json
"url": " https://keyflow-backend-62hevvkvea-uc.a.run.app/api/trigger/vapi/webhook"

Notice there's a space character at the beginning of the URL, before "https://". The validation is failing because it's expecting a valid URL that starts with either "https://" or "wss://", but instead it's finding " https://" (with a leading space). To fix this issue, you need to remove the leading space from the URL value in your request, so it should be:

json
"url": "https://keyflow-backend-62hevvkvea-uc.a.run.app/api/trigger/vapi/webhook"

Leading or trailing whitespace in URL fields often causes validation issues like this, especially in JSON payloads where every character is significant.

🤦‍♂️ that was a stupid error on our part. Thanks @User for the help. Appreciate it