This is a simple workflow - ask user their name and then call the API with the user_name in parameter called utterance. This is what I receive at the server: [VAPI Message] {"type": "workflow.node.started", "node": {"type": "tool", "name": "apiRequest_1754842953282", "tool": {"type": "apiRequest", "function": {"name": "apiRequest-954f8956", "description": "Use this to make an API request to .", "parameters": {"type": "object", "properties": {"agency_id": {"type": "string", "default": "{{agency_id}}", "description": ""}, "utterance": {"type": "string", "default": "{{user_name}}", "description": ""}}, "required": []}}, "body": {"type": "object", "properties": {"agency_id": {"type": "string", "default": "{{agency_id}}", "description": ""}, "utterance": {"type": "string", "default": "{{user_name}}", "description": ""}}, "required": []}, "method": "POST", "url": ", "headers": {"type": "object", "properties": {"Authorization": {"type": "string", "value": "Bearer [REDACTED]"}}}, "messages": [{"type": "request-start", "contents": [], "conditions": [], "blocking": false}], "variableExtractionPlan": {"schema": {"type": "object", "required": [], "properties": {}}, "aliases": []}}, "metadata": {"position": {"x": -464.66666666666663, "y": 145.03924680857477}}}} https://cdn.discordapp.com/attachments/1211484481848873020/1404140047812526171/Screenshot_2025-08-10_172707.png?ex=689a1ad3&is=6898c953&hm=823d074f2b41c7332759602e4511ed4b9c50f1a274864fd5f8fd25a2641ab8dd&

Variables only work if passed via workflowOverrides.variableValues in a webhook response or assistantOverrides.variableValues when starting from an assistant, direct workflow calls can't use dynamic variables yet..

I am new to VAPI so please forgive if this is naive. Does that mean if I were to setup a webhook and call that webhook from the workflow using API request node, then VAPI will recognize those variables and be able to pass them back to my backend in the API calls? That makes it impossible to use dynamic variable that are captured during the conversation

If you set up a webhook and call it from a vapi workflow’s API Request node using variables like {{variable_name}}, vapi will replace them with actual values at runtime and send them to your backend in the API call..

Thank you!