Free Calendly alternative built on WhatsApp + Google Calendar. Built with FastAPI + Twilio + Google Calendar API.
Customer WhatsApp
│
▼
Twilio API
│ POST /webhook/{host_slug}
▼
FastAPI App
│
├─► Conversation State Machine
│ (IDLE → NAME → SERVICE → DATE → SLOT → CONFIRM → DONE)
│
├─► Google Calendar API
│ (check free slots, create/cancel events)
│
└─► SQLite DB
(hosts, bookings, sessions)
git clone https://github.com/you/wa-scheduler
cd wa-scheduler
pip install -r requirements.txt
cp .env.example .env- Sign up at https://twilio.com
- Go to Messaging → Try it out → Send a WhatsApp message
- Note your sandbox number (e.g., +14155238886)
- Set webhook URL to:
https://YOUR_URL/webhook/YOUR_SLUG
- Go to https://console.cloud.google.com
- Create project → Enable Google Calendar API
- Create OAuth 2.0 Client ID (Web application)
- Add redirect URI:
https://YOUR_URL/auth/google/YOUR_SLUG/callback - Download JSON → save as
client_secrets.json
TWILIO_ACCOUNT_SID=ACxxx
TWILIO_AUTH_TOKEN=xxx
GOOGLE_CLIENT_SECRETS_FILE=./client_secrets.json
BASE_URL=https://your-public-url.com
ADMIN_KEY=your-secret-keypython start.pycurl -X POST http://localhost:8000/dashboard/register \
-H "x-api-key: your-secret-key" \
-H "Content-Type: application/json" \
-d '{
"slug": "dr-sharma",
"business_name": "Dr. Sharma Clinic",
"owner_phone": "+919876543210",
"location": "123 MG Road, Pune",
"services": [
{"name": "Consultation", "duration_mins": 30, "price": 500},
{"name": "Follow-up", "duration_mins": 15, "price": 200}
],
"working_days": [0,1,2,3,4,5],
"working_hours": {"start": "09:00", "end": "18:00"}
}'Visit: https://YOUR_URL/auth/google/dr-sharma
Business owner clicks "Allow" → calendar connected.
Customer: "Hi"
Bot: "Welcome to Dr. Sharma Clinic! What's your name?"
Customer: "Ravi Kumar"
Bot: "Great, Ravi! Choose a service:
1. Consultation (30 min) — ₹500
2. Follow-up (15 min) — ₹200"
Customer: "1"
Bot: "Choose a date:
1. Monday, 21 April (Today)
2. Tuesday, 22 April
3. Wednesday, 23 April ..."
Customer: "2"
Bot: "Available slots on Tuesday, 22 April:
1. 9:00 AM 2. 10:00 AM 3. 2:00 PM ..."
Customer: "3"
Bot: "Booking Summary:
Name: Ravi Kumar | Service: Consultation
Date: Tuesday, 22 April | Time: 2:00 PM
Reply YES to confirm."
Customer: "YES"
Bot: "✅ Booking Confirmed! See you Tuesday at 2 PM.
Type 'cancel' to cancel, 'reschedule' to change."
| Service | Free Tier | Use For |
|---|---|---|
| Railway.app | 500 hrs/mo | FastAPI server |
| Twilio Sandbox | Free for testing | WhatsApp gateway |
| Twilio Paid | $1/mo + $0.005/msg | Production WhatsApp |
| SQLite (local) | Free forever | <10k bookings |
| Supabase Postgres | 500MB free | Scale up |
Monthly cost for 100 active users: ~₹200–400 (Twilio messages only)
# Install Railway CLI
npm install -g @railway/cli
railway login
railway init
railway up
railway domain # get your public URLAdd environment variables in Railway dashboard.
| Endpoint | Method | Description |
|---|---|---|
/webhook/{slug} |
POST | Twilio WhatsApp webhook |
/auth/google/{slug} |
GET | Start Google OAuth |
/dashboard/register |
POST | Register new business |
/dashboard/{slug}/bookings |
GET | View bookings |
/dashboard/{slug}/stats |
GET | Booking stats |
/docs |
GET | Swagger UI |
Free tier: 1 business, 50 bookings/mo → ₹0
Starter: 3 businesses, unlimited → ₹299/mo
Pro: Unlimited + analytics → ₹999/mo
White label: Custom domain + branding → ₹2999/mo
Comparable: Calendly charges $8–16/user/month = ₹700–1400/mo Your pricing at 1/5th of Calendly with WhatsApp-first = massive India advantage.
Target customers:
- Doctors & clinics (no-show reduction alone = sold)
- Tutors & coaching centers
- Salons & beauty parlors
- Consultants & lawyers
- Any business taking appointments on WhatsApp today (manual process)
- Reminder messages (24hr + 1hr before)
- Cancellation waitlist (notify next person)
- Recurring appointments
- Payments via Razorpay/UPI before confirmation
- Hindi/Marathi language mode
- Web dashboard for business owners
- SMS fallback for non-WhatsApp users