AI email responder: draft Gmail replies automatically with n8n

Trigger and agent

1. Create workflow, Add first step, search gmail. Under Triggers, pick On message received.
2. Connect the business inbox with Sign in with Google. Keep Every Minute and click Fetch Test Event.
3. Add AI Agent. Set Source for Prompt to Define below and paste the prompt below.
4. Chat Model: OpenAI Chat Model with your OpenAI account credential.

The prompt

Write a reply to this email, then save it as a draft in the same thread.
<email>
From: {{ $json.From }}
Subject: {{ $json.Subject }}
Message: {{ $json.snippet }}
</email>

The {{ }} parts pull in each email's sender, subject and message.

Gmail Tool: drafts only

Resource

Change Message to Draft. Operation switches to Create.

Subject

Re: {{ $json.Subject }}

Message

Click ✦ so the model writes it.

Thread ID

{{ $json.threadId }}, so the draft sits under the customer's email.

To Email

{{ $json.From }}, so you can just hit send.

Facts, then the fix

• Add Simple Memory, then a System Message in four parts: who you are, what you know, rules, how to write.
• Rules: only create drafts. If it doesn't know, say someone from the team will follow up. Never make up prices, dates or services.
• No session ID found in Simple Memory? Set Session ID to Define below and paste {{ $json.threadId }}.
• All green? Read the draft in Gmail, then click Publish.