Instagram DM reply bot with ManyChat and an OpenAI agent

What it is

This n8n workflow is the brain behind an Instagram message bot. ManyChat, the chat tool that sits between Instagram and n8n, posts each incoming message to a webhook, together with an id for that chat. A Set step holds your system prompt and picks the message text and the chat id out of the request. An OpenAI agent writes the answer in the voice the prompt describes, and a window memory keeps the recent turns of each chat. The workflow then hands the answer back as JSON. Six nodes run it, beside one sticky note.

Who it suits

Creators and small brands who get the same questions in their Instagram inbox and want a first reply in their own tone. Skip it if a wrong answer would cost money or trust, because the bot knows only what your prompt tells it. It writes to real people.

You need to know n8n’s settings: import a file, add one credential, set a webhook live and call it from another tool.

Where to use it

It needs an n8n that ManyChat can reach over the internet, and a ManyChat account connected to Instagram.

• n8n Cloud: import the file and publish it, then use the production webhook address
• Your own n8n server: the same file and steps, with the webhook reachable from the internet over https
• ManyChat: a flow that posts each message to that address and shows the reply
• OpenAI: the model that writes the replies

Setup

Download saves a zip with workflow.json and Mindket’s setup notes in your downloads folder. Setup is one credential, one prompt and one address in ManyChat.

1. In n8n, create a workflow, open its menu, choose Import from File and pick workflow.json.
2. Add an OpenAI credential and select it in OpenAI Chat Model.
3. Open Set System Prompt. Replace <YOUR_EXAMPLE_POSTS> with your own posts, and change the rules if you like.
4. Publish the workflow, open Receive Instagram Message and copy its production address.
5. In ManyChat, add a request step that posts JSON to that address. Send a value that is unique to each contact as session_id, and the contact’s last message as text. Show the output field of the reply as the bot’s message.

How to use it

Leave the workflow published. Each message a follower sends in the ManyChat flow gets a reply that the agent writes. Test with your own account before you open it to everyone.

Example

A follower asks your bot a question through the ManyChat flow.

{"session_id": "1001", "text": "What is your top tip for starting out?"}

The agent answers in a short line, in the voice of your example posts, and the webhook returns a JSON object with one field called output. ManyChat shows that text to the follower.

For newcomers and experts

If you are new. n8n draws a workflow as boxes joined by lines, and each box, a node, does one job. This one waits for a message, asks an AI to answer it and sends the answer back. Add your example posts first, because the bot only knows what you give it.

For experts. The chat id from ManyChat is the memory key.

Good to know

The webhook is open, so treat it like a door with no lock.

• Safety: anyone who finds the address can send messages and spend your OpenAI credit. Switch the webhook’s authentication to a header check and send the same header from ManyChat, if ManyChat lets you add one
• Fixes: the original set no model, so n8n would have used its default, gpt-5-mini, which OpenAI shuts down on 11 December 2026. The model is now gpt-5.6-terra. The prompt is rewritten, with a placeholder for your posts, and the webhook address is neutral
• Limits: the bot knows only what the prompt tells it. It is told to say so when it does not know, which lowers the risk of a made-up answer and does not remove it
• Memory: it lives in the n8n process, so a restart clears every chat. The last turns are all it keeps
• Cost and data: each message is one OpenAI call, and the chat text goes to OpenAI
• Not run: Mindket did not run it against ManyChat, Instagram or OpenAI, and did not check ManyChat’s screens, its limits or how long it waits for a reply
• Credentials: the JSON holds none