Show HN: A free FAQ and appointment booking API for small businesses

Use your business's CallChatSyn answering bot and booking calendar from your own website, app or AI agent. Same answers your customers get on WhatsApp and your booking page. Machine-readable spec: openapi.json.

Founder offer: free for the first 1,000 businesses

Answering bot, order status and bookings through the API on any plan, with no trial expiry (up to 100 API calls a day, 2,000 a month). Building for clients? Each client business claims its own spot.

1. Create a free account and confirm your email.
2. Add your FAQs and opening hours (2 minutes).
3. Open Dashboard → Developers, click Claim founder API access , and create a key.

Try it now, no sign-up #

Use the public demo key ccs_demo_public with any example below. It answers as our demo business, and bookings are dry runs: you see the time would be booked, but nothing is saved. It's shared by everyone, so it allows 500 calls a day in total.

curl https://callchatsyn.com/api/v1/answer \
  -H "Authorization: Bearer ccs_demo_public" \
  -H "Content-Type: application/json" \
  -d '{"message": "Where are you located?"}'

1. Get a key #

In Dashboard → Developers, create a key. It's shown once; keep it on your server, never in browser code. Send it on every request as Authorization: Bearer ccs_live_….

2. Answer a customer's message #

curl https://callchatsyn.com/api/v1/answer \
  -H "Authorization: Bearer $CCS_KEY" \
  -H "Content-Type: application/json" \
  -d '{"message": "What are your opening hours?"}'

3. Book an appointment #

curl https://callchatsyn.com/api/v1/slots -H "Authorization: Bearer $CCS_KEY"

curl https://callchatsyn.com/api/v1/bookings \
  -H "Authorization: Bearer $CCS_KEY" -H "Content-Type: application/json" \
  -d '{"start":"2026-10-10T02:00:00.000Z","service":"Haircut","name":"Ana","email":"ana@example.com"}'

Use it from an AI assistant (MCP) #

The open-source callchatsyn-mcp server gives Claude, Cursor and other MCP clients three tools: answer a customer question, list open times, book an appointment.

{
  "mcpServers": {
    "callchatsyn": {
      "command": "npx",
      "args": ["-y", "github:oneappsworld/callchatsyn-mcp"],
      "env": { "CALLCHATSYN_API_KEY": "ccs_live_..." }
    }
  }
}

Errors and limits #

• Errors look like {"error":{"code":"…","message":"…"}} .
• With the demo key, POST /api/v1/bookings returns 200 with{"booked":false,"demo":true} instead of booking.
• 401 bad key · 402 plan inactive · 403 feature not in plan · 429 usage limit · 400/404/409 request problems.
• Each request counts toward the business's plan limits, the same as WhatsApp and booking-page messages.
• The answering bot, order status and bookings are included on the Pro plan. Founder offer: the first 1,000 businesses to claim it in Dashboard → Developers get them free on any plan (up to 100 API calls a day, 2,000 a month).