n8n Gmail Trigger: Auto Schedule Appointments with GPT-4

Automatically turn Gmail appointment emails into scheduled-ready replies (with GPT-4 + Google Calendar)

This n8n workflow monitors your unread Gmail messages, uses OpenAI (GPT-4) to detect appointment requests, checks your Google Calendar availability for the next month, and then emails back a proposed meeting time—complete with a buffer around your existing events.

What this workflow does

• Polls Gmail every minute for unread emails (excluding spam and trash).
• Sends the email subject and snippet to OpenAI to classify whether the message is an appointment or a call request.
• If it’s an appointment request, an OpenAI agent retrieves your upcoming confirmed Google Calendar events for the next month.
• Filters, formats, and sorts the calendar data, then returns it to the agent as a JSON string of busy time ranges.
• The agent drafts an email reply proposing a specific meeting time, including a 15-minute buffer around existing meetings.
• Replies to the original Gmail thread and marks the message as read.

Use cases

• Speed up scheduling when prospects email you with “Can we meet next week?”
• Reduce back-and-forth by automatically suggesting time slots based on real availability.
• For SaaS operators and automation engineers: standardize appointment handling across a mailbox.

Technical details

• n8n Gmail Trigger: polls every minute for unread messages (excluding spam/trash).
• if / set: routing and message preparation for classification and reply logic.
• OpenAI (GPT-4): classifies appointment vs call, then powers the scheduling agent.
• Google Calendar (OAuth2): pulls confirmed busy events for the next month from the configured calendar identifier (currently `your_email@gmail.com`).
• Filtering & JSON formatting: converts calendar events into structured busy ranges the agent can use.
• Reply & mark-as-read: sends the proposed times and updates Gmail message status.