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.
- 1. 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
- 2. 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.
- 3. 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: bookAppointment
- 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 message.toolCalls[0].function.name
. If the names differ, nothing will run.
C) Configure availability
Open 1. CONFIGURATION (EDIT ME) and set:
timeZone
(e.g. America/New_York
)
workdayStartHour
/ workdayEndHour
(24h integers)
meetingDurationMinutes
(e.g. 30
or 60
)
bufferBeforeMinutes
/ bufferAfterMinutes
(e.g. 15
)
bookingCadenceMinutes
(e.g. 30
)
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.