Initiate an outbound Vapi AI voice agent call, pass dynamic variables to the assistant, and handle function-call webhooks mid-call

Steps

1. Create or retrieve an assistant configuration via POST /assistant with model, voice, firstMessage, and a functions array describing callable tools the agent can invoke during a call
2. Initiate an outbound call via POST /call/phone with assistantId (or inline assistantOverrides), phoneNumberId, and the customer's phoneNumber in the request body
3. Include a variableValues map in the request body to inject dynamic data (customer name, order number, account details) into the assistant's system prompt at call time
4. Expose a public HTTPS endpoint to receive function-call webhook payloads — when the agent calls a defined function, Vapi POSTs the call ID, function name, and arguments to your serverEndpoint URL
5. Respond to the webhook within the timeout window with a result object so Vapi can relay the data back to the agent's LLM context and continue the conversation
6. Retrieve call metadata and transcript via GET /call/{callId} after the call ends to store results in your CRM