Automated Voice Appointment Booking with Vapi AI and Google Calendar

Description

What this template does

Connect a Vapi AI voice agent to Google Calendar to capture contact details and auto-book appointments.
The agent asks for name, address, service type, and a preferred time. The workflow checks availability and either proposes times or books the slot—no code needed.

How it works (node map)

Webhook: Production URL = VAPI Server URL — receives tool calls from Vapi and returns results.
CONFIGURATION (EDIT ME)** — your timezone, work hours, meeting length, buffers, and cadence.
Route by Tool Name** — routes Vapi tool calls:
checkAvailability → calendar lookup path
bookAppointment → create event path
Get Calendar Events (EDIT ME)** — reads events for the requested day.
Calculate Potential Slots / Filter for Available Slots** — builds conflict-free options with buffers.
Respond with Available Times — returns formatted slots to Vapi.
Book Appointment in Calendar (EDIT ME)** — creates the calendar event with details.
Booking Confirmation** — returns success back to Vapi.

> Sticky notes in the canvas show exactly what to edit (required by n8n).
No API keys are hardcoded; Google uses OAuth credentials.

Requirements

n8n (Cloud or self-hosted)
Google account with Calendar (OAuth credential in n8n)
Vapi account + one Assistant

Setup (5 minutes)
A) Vapi → n8n connection

Open the Webhook node and copy the Production URL.
In Vapi → Assistant → Messaging, set Server URL = that Production URL.
In Server Messages, enable only toolCalls.

B) Vapi tools (names must match exactly)

Create two Custom Tools in Vapi and attach them to the assistant:

Tool 1: checkAvailability

Arguments**
initialSearchDateTime (string, ISO-8601 with timezone offset, e.g. 2025-09-09T09:00:00-05:00)

Tool 2:
Arguments**
startDateTime (string, ISO-8601 with tz)
endDateTime (string, ISO-8601 with tz)
clientName (string)
propertyAddress (string)
serviceType (string)

> The Switch node routes based on
C) Configure availability

Open 1. CONFIGURATION (EDIT ME) and set:

D) Connect Google Calendar

Open 2. Get Calendar Events (EDIT ME) → Credentials: select/create Google Calendar OAuth.
Then choose the calendar to check availability.
Open 3. Book Appointment in Calendar (EDIT ME) → use the same credential and same calendar to book.

E) Activate & test

Toggle the workflow Active.
Call your Vapi number (or start a session) and book a test slot.
Verify the event appears with description fields (client, address, service type, call id).

Customising

Change summary/description format in 3. Book Appointment.
Add SMS/Email confirmations, CRM sync, rescheduling, or analytics as follow-ups (see sticky note “I’m a note”).

Troubleshooting

No response back to Vapi** → confirm Vapi is set to send toolCalls only and the Server URL matches the Production URL.
Switch doesn’t route** → tool names must be exactly checkAvailability and bookAppointment.
No times returned** → ensure timezone + work hours + cadence generate at least one future slot; confirm Google credential and calendar selection.
Event not created** → use the same Google credential & calendar in both nodes; check OAuth scopes/consent.

Security & privacy

Google uses OAuth; credentials live in n8n.
No API keys hardcoded.
Webhook receives only the fields needed to check times or book.