VAPI•3mo ago

500 Error When Creating Customer with assistantOverride

Hi VAPI Support Team,

I’m encountering an issue when creating Customer objects via the API.

The request works successfully when I include only name and number, but it returns a 500 Internal Server Error whenever I include assistantOverrides.variableValues.

orgId: 727f8c9d-9632-4e41-9268-1919aa9c97c7

Below are the details:

=====================================================

This works:

Request:POST https://api.vapi.ai/customer

{
"name": "jonny",
"number": "+19174761638"
}
Response:

{
"id": "87011052-9735-41bd-93d2-5b4422b56365",
"orgId": "727f8c9d-9632-4e41-9268-1919aa9c97c7",
"number": "+19174761638",
"createdAt": "2025-10-08T01:32:13.207Z",
"updatedAt": "2025-10-08T01:32:13.207Z",
"name": "jonny"
}

==================================================

This fails:

Request:POST https://api.vapi.ai/customer

{
"name": "jonny",
"number": "+19174761638",
"assistantOverrides": {
"variableValues": {
"Cur_State": "NY"
}
}
}
Response:

{
"statusCode": 500,
"message": "Internal server error. Contact support@vapi.ai for help."
}

=================================================
Could you please confirm what am I missing?
Thank you for your help!

Best regards,
Ronak Shah
shah.ronak@columbia.edu

thoughtless-moccasinOP•10/8/25, 1:42 AM

@Duckie

Vapi Support BotAPP•10/8/25, 1:43 AM

It appears that the assistantOverridesassistantOverrides property—especially with variableValuesvariableValues—may not be supported when creating a customer via the /customer/customer endpoint, as most documentation examples use it in call or campaign creation contexts. As a next step, try creating the customer without assistantOverridesassistantOverrides, then apply personalization at the call level:

{
  "assistantId": "your-assistant-id",
  "assistantOverrides": {
    "variableValues": {
      "Cur_State": "NY"
    }
  },
  "customer": {
    "id": "customer-id"
  },
  "phoneNumberId": "your-phone-id"
}

{
  "assistantId": "your-assistant-id",
  "assistantOverrides": {
    "variableValues": {
      "Cur_State": "NY"
    }
  },
  "customer": {
    "id": "customer-id"
  },
  "phoneNumberId": "your-phone-id"
}

Apply dynamic variables when starting a call, not during customer creation. If you need to personalize at the customer level, please contact support@vapi.ai for confirmation on schema support or possible workarounds.

Sources:

⤵️ Mention @Vapi Support Bot for follow-ups 🐥

Vapi Support BotAPP•10/8/25, 1:43 AM

Thank you for the detailed information! To help diagnose the 500 error, could you confirm whether the variable Cur_StateCur_State is defined in your assistant's configuration as a dynamic variable? If not, the API may not recognize it, which can cause errors.

If you’re unsure, please check your assistant setup for a list of supported variables or let me know if you need guidance on where to find this in the dashboard.

Example variable definition in assistant config:

{{Cur_State}}

{{Cur_State}}

Let me know if Cur_StateCur_State is present or if you need help checking this!

Source:

Dynamic Variables Documentation

Tthoughtless-moccasin Hi VAPI Support Team, I’m encountering an issue when creating Customer objects ...

exclusive-coral•10/8/25, 4:30 AM

Hey Ronak, I can help you fix this. The 500 error often happens when the variable isn’t defined in the assistant’s settings. Can you confirm if your assistant includes Cur_State as a variable? Once I know that, I’ll assist you with the correct payload format.
@ronaks2309

thoughtless-moccasinOP•10/8/25, 7:58 AM

Hi @LordXcel Thanks for your prompt response. I'm only using this custom variable in the System Prompt like {{Cus_State}}. Not sure where I can define this variable in the assistant... Happy to go over this on DM

500 Error When Creating Customer with assistantOverride

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