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

CallChatSyn launched a free public API that lets small businesses expose their answering bot, order status and booking calendar to websites, apps and AI agents, with founder access free for the first 1,000 businesses at up to 100 API calls a day and 2,000 a month. The API is documented with an OpenAPI spec and a public demo key, ccs_demo_public, that allows 500 calls a day in total and returns dry-run bookings, and an open-source MCP server, callchatsyn-mcp, gives Claude, Cursor and other MCP clients three tools for answering questions, listing open times and booking appointments.

CallChatSyn API 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 https://callchatsyn.com/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 https://callchatsyn.com/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?"}' {"intent":"faq","lang":"en","matched":true,"reply":"We're open every day, 9am to 9pm."} 3. Book an appointment curl https://callchatsyn.com/api/v1/slots -H "Authorization: Bearer $CCS KEY" {"slots": {"start":"2026-10-10T02:00:00.000Z","label":"Sat 10 Oct, 10:00"} ,"services": "Haircut" ,"locations": "Main St" } 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"}' 201 {"booked":true,"start":"2026-10-10T02:00:00.000Z","label":"Sat 10 Oct, 10:00"} Use it from an AI assistant MCP The open-source callchatsyn-mcp https://github.com/oneappsworld/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 .