Handle Vapi voice agent tool calls and call logging with Google Sheets and Gmail

Quick overview

This workflow provides a backend webhook for Vapi voice agents, handling mid-call tool calls via Google Calendar and Google Sheets, then logging end-of-call details to Google Sheets and sending follow-up alerts through Gmail when keywords are detected.

How it works

1. Receives a POST request from Vapi through a single webhook for both tool calls and end-of-call reports.
2. Normalizes the incoming payload to extract the event type, tool call details, caller number, call ID, transcript, summary, and call metadata.
3. For mid-call tool requests, routes by function name to either check Google Calendar availability, look up a customer in Google Sheets, append a request to Google Sheets, or return a safe response for unknown functions.
4. Formats the selected tool result into Vapi’s required { results: [{ toolCallId, result }] } response and returns it immediately to the caller.
5. For end-of-call reports, extracts a call record, scans the transcript and summary for configured follow-up keywords, and prepares flags.
6. Appends the call record to a Google Sheets “Calls” tab and sends a Gmail alert email only if the call is flagged as needing follow-up, then acknowledges receipt to Vapi.

Setup

1. Create Google Calendar, Google Sheets, and Gmail credentials in n8n.
2. Update the Agent Config values (CalendarId, AlertEmail, SlotLengthMinutes, TransferMessage, and FollowUpKeywords) to match your environment.
3. Create a Google Sheets spreadsheet with “Customers”, “Requests”, and “Calls” tabs (and matching column headers) and replace YOUR_SPREADSHEET_ID in all Google Sheets steps.
4. Activate the workflow, copy the production webhook URL, and set it as the Server URL in your Vapi assistant.
5. In Vapi, define tools named check_availability, lookup_customer, and log_request (and optionally transfer_call if you want the custom transfer message).