My calls are inititated from my CRM with Name, Number, ExternalId (the ID in my crm). During the call I have a tool which uses the customer's externalId to update the record in the CRM. It fails everytime. When the API request is made to our CRM the ExternalId isn't being sent, instead it is sending the placeholder {{externalId}}. For example: [ {"ID":"{{externalId}}", "f_59461192":"2025-10-17", "f_59461193":"14:00"} ] I'm trying to send batches of calls so each custmer will have a different externalId: { "assistantId": "50e81872-dde1-4099-bacd-9dd4fed8eb5c", "phoneNumberId": "27914252-33ca-4e9f-84f7-d9dcaa074f67", "customers": [ { "number": "+4412345678", "name": "Matt", "externalId": "2613" }, { "number": "+440292999292", "name": "James", "externalId": "2614" } ] } Example calls 0199ee65-4bf9-755a-874e-143c310cec54 0199ee47-aa3f-7449-91db-cf4ae425d9e2

To ensure

externalId

is accessible as a variable during your call, explicitly set it in the

assistantOverrides.variableValues

for each customer. For batch calls, you should call the endpoint separately for each customer if you need unique variables. Example:

json
{
  "assistantId": "your-assistant-id",
  "phoneNumberId": "your-phone-number-id",
  "customer": {
    "number": "+4412345678"
  },
  "assistantOverrides": {
    "variableValues": {
      "externalId": "2613"
    }
  }
}

Reference

{{externalId}}

in your tool's API request body to ensure it is replaced properly. According to the documentation, arbitrary fields like

externalId

are not automatically mapped—set them explicitly in

variableValues

for each call to avoid placeholder issues. Source: - [Personalization with user information](https://docs.vapi.ai/assistants/personalization)

What about in a campaign?

Hi James, To obtain the

callId

in VAPI, you can access it through webhooks or API responses where call information is provided. If you are working with test suite runs, the recent update allows you to include

callId

in a [TestSuiteRunTestAttempt](https://docs.vapi.ai/changelog/2025/3/30). For direct access in workflows or UI, ensure your webhook endpoint/parsing logic captures the necessary data, as IDs are often part of the payload for events like

call.deleted

or

call.delete.failed

. If you're using a specific tool or integration (e.g., MCP tool), make sure to follow the related documentation for handling these identifiers. You may also want to consider looking at session properties or metadata if you're tracking call details comprehensively. Let me know if you need more detailed instructions for a specific context.