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Voice-driven AI assistant using VAPI and GPT-4.1-mini with memory

Robert BreenRobert Breen
699 views
2/3/2026
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Send VAPI voice requests into n8n with memory and OpenAI for conversational automation

This template shows how to capture voice interactions from VAPI (Voice AI Platform), send them into n8n via a webhook, process them with OpenAI, and maintain context with memory. The result is a conversational AI agent that responds back to VAPI with short, business-focused answers.


โœ… What this template does

  • Listens for POST requests from VAPI containing the session ID and user query
  • Extracts session ID and query for consistent conversation context
  • Uses OpenAI (GPT-4.1-mini) to generate conversational replies
  • Adds Memory Buffer Window so each VAPI session maintains history
  • Returns results to VAPI in the correct JSON response format

๐Ÿ‘ค Whoโ€™s it for

  • Developers and consultants building voice-driven assistants
  • Businesses wanting to connect VAPI calls into automation workflows
  • Anyone who needs a scalable voice โ†’ AI โ†’ automation pipeline

โš™๏ธ How it works

  1. Webhook node catches incoming VAPI requests
  2. Set node extracts session_id and user_query from the request body
  3. OpenAI Agent generates short, conversational replies with your business context
  4. Memory node keeps conversation history across turns
  5. Respond to Webhook sends results back to VAPI in the required JSON schema

๐Ÿ”ง Setup instructions

Step 1: Create Function Tool in VAPI

  1. In your VAPI dashboard, create a new Function Tool
    • Name: send_to_n8n
    • Description: Send user query and session data to n8n workflow
    • Parameters:
      • session_id (string, required) โ€“ Unique session identifier
      • user_query (string, required) โ€“ The userโ€™s question
    • Server URL: https://your-n8n-instance.com/webhook/vapi-endpoint

Step 2: Configure Webhook in n8n

  1. Add a Webhook node
  2. Set HTTP method to POST
  3. Path: /webhook/vapi-endpoint
  4. Save, activate, and copy the webhook URL
  5. Use this URL in your VAPI Function Tool configuration

Step 3: Create VAPI Assistant

  1. In VAPI, create a new Assistant
  2. Add the send_to_n8n Function Tool
  3. Configure the assistant to call this tool on user requests
  4. Test by making a voice query โ€” you should see n8n respond

๐Ÿ“ฆ Requirements

  • An OpenAI API key stored in n8n credentials
  • A VAPI account with access to Function Tools
  • A self-hosted or cloud n8n instance with webhook access

๐ŸŽ› Customization

  • Update the system prompt in the OpenAI Agent node to reflect your brandโ€™s voice
  • Swap GPT-4.1-mini for another OpenAI model if you need longer or cheaper responses
  • Extend the workflow by connecting to CRMs, Slack, or databases

๐Ÿ“ฌ Contact

Need help customizing this (e.g., filtering by campaign, connecting to CRMs, or formatting reports)?

  • ๐Ÿ“ง rbreen@ynteractive.com
  • ๐Ÿ”— https://www.linkedin.com/in/robert-breen-29429625/
  • ๐ŸŒ https://ynteractive.com

Voice-Driven AI Assistant using Vapi and GPT-4.1 Mini with Memory

This n8n workflow demonstrates how to build a voice-driven AI assistant that leverages Vapi for real-time voice interaction, an OpenAI Chat Model (likely GPT-4.1 Mini based on the directory name hint) for conversational AI, and a simple memory buffer to maintain context.

The workflow acts as a backend for a voice assistant, receiving user input via a webhook, processing it with an AI agent, and responding with a generated message. The "Simple Memory" node ensures that the AI agent can remember previous turns in the conversation, leading to more coherent and natural interactions.

What it does

  1. Listens for Voice Input: Initiates when a Webhook receives an incoming request, typically from a voice interaction platform like Vapi, containing user's spoken input.
  2. Sets Initial Data: An Edit Fields (Set) node is present, though its specific configuration isn't detailed in the JSON, it's typically used to structure or transform the incoming webhook data for subsequent nodes.
  3. Maintains Conversation Context: A Simple Memory node (likely a Buffer Window Memory) stores previous parts of the conversation, allowing the AI to recall past interactions.
  4. Processes with AI Agent: An AI Agent node (from LangChain) orchestrates the interaction with the language model, using the provided memory to generate intelligent responses.
  5. Generates AI Response: An OpenAI Chat Model node (from LangChain) is the core language model, taking the user's input and conversational history to generate a relevant and natural language response.
  6. Responds to Voice Platform: The Respond to Webhook node sends the AI-generated response back to the initiating voice platform (e.g., Vapi) to be spoken back to the user.

Prerequisites/Requirements

  • n8n Instance: A running n8n instance (self-hosted or cloud).
  • OpenAI API Key: An API key for OpenAI to use their chat models (e.g., GPT-4.1 Mini). This will need to be configured as a credential in n8n for the OpenAI Chat Model node.
  • Vapi Account (or similar voice platform): A voice API platform that can send webhook requests and receive responses. The webhook URL from this n8n workflow will need to be configured in your Vapi assistant.
  • LangChain Nodes: Ensure the @n8n/n8n-nodes-langchain package is installed in your n8n instance.

Setup/Usage

  1. Import the Workflow: Import the provided JSON into your n8n instance.
  2. Configure Webhook:
    • Activate the Webhook node.
    • Copy the "Webhook URL" provided by the node.
    • Paste this URL into your Vapi assistant configuration (or whichever voice platform you are using) as the endpoint for handling user input.
  3. Configure OpenAI Credentials:
    • Click on the OpenAI Chat Model node.
    • Select or create a new "OpenAI API" credential.
    • Enter your OpenAI API Key.
  4. Configure AI Agent and Memory:
    • Review the AI Agent and Simple Memory nodes to ensure their configurations (e.g., model name, memory window size) meet your requirements. The OpenAI Chat Model will likely be set to a model like gpt-4-1106-preview or gpt-3.5-turbo by default, but you can adjust it.
  5. Activate the Workflow: Save and activate the workflow.

Once activated, your voice assistant should be ready to receive voice input via Vapi (or your chosen platform), process it with the AI, and respond in real-time.

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