----------------------------- **While I generate an answer, here are some sources that might be helpful**: * [Create Phone Call]() * [Glossary]() * [Server URLs]() * [List Calls]() -----------------------------

### Answer It looks like you might be encountering an issue related to how parameters are named and passed in the webhook payload. According to the Vapi documentation, parameters need to be formatted correctly when sending to the webhook. 1. Ensure that you have registered the correct server URL to receive the webhook events from Vapi [(1)]() . 2. When defining the parameters in your assistant, make sure they match the expected format in the webhook. For example, if the webhook expects

phone_number

, use

phone_number

without curly braces. 3. If you are experiencing issues with parameter names being sent in the wrong format, like "start_time" vs. "startTime", this could be due to model hallucination. A possible solution is to handle both formats within your webhook [(2)]() . Here is an example of how to define and send the payload correctly in cURL:

shell
curl --request POST \
--url https://api.vapi.ai/call/phone \
--header 'Authorization: Bearer <your_token>' \
--header 'Content-Type: application/json' \
--data '{
  "customer": {
    "number": "your_phone_number"
  },
  "phoneNumber": {
    "twilioPhoneNumber": "your_twilio_number"
  },
  "assistantId": "your_assistant_id",
  "serverUrl": "your_server_url",
  "metadata": {
    "phone_number": "1234567890"
  }
}'

[(1)]() , [(2)]() Make sure the

serverUrl

is correctly set up to receive and handle the incoming data. If you continue to experience issues, double-check the webhook logs to see if the payload is being received and processed as expected.

Got it. Tagging @User for additional help.