I’m working on an app that needs to automatically create bookings on users’ Calendly accounts. My backend should be able to check available time slots and make reservations without manual input.
I think users will need to give my app some kind of access token, but I’m having trouble understanding Calendly’s docs. They don’t clearly explain how external applications can use their API to book appointments on behalf of users.
Has anyone successfully implemented this kind of third-party booking system? What’s the proper way to authenticate and create meetings through their API endpoints?
Been there, done that. Built something similar for our customer portal last year.
Start with OAuth 2.0. Users authorize your app through Calendly’s consent screen, you get an access token for API calls.
Here’s how it works:
Send users to Calendly’s authorization URL
They grant permission, get redirected back with auth code
Exchange code for access token
Use token to hit scheduling endpoints
For bookings, use /scheduled_events. Heads up though - you can’t create bookings directly. Get their event types first, then available slots, then POST the booking.
Store tokens securely and refresh when they expire. Calendly tokens last pretty long but don’t skip refresh logic.
This video breaks down API key setup really well:
One gotcha - use the right API version. Their v1 endpoints are getting phased out, so stick with v2.
calendly webhooks r tricky but doable. first, register your webhook URLs in their dev console. then handle the POST requests when someone books. make sure to verify those webhook signatures - otherwise you’ll get bogus booking data. their sandbox acts weird sometimes, so be careful when testing in prod.
I’ve worked with Calendly’s API for a client management system, and their event-based setup has some quirks. Get OAuth running first, then dive into the /event_types endpoint. Each user’s appointment types come with preset configs - duration, availability, buffer times - and you can’t override them when booking. Don’t try to create bookings directly. Instead, use /scheduling_links to generate unique links for each request, then track the actual bookings via webhooks. This keeps you in sync with their availability engine and prevents conflicts. Rate limiting hits hard with multiple users. Set up request queuing early because their limits are tighter than what’s documented. Cache event type data too - it doesn’t change much but gets hammered with requests. Token management is pretty standard, just watch expiration dates closely. Calendly won’t always warn you before tokens die, unlike other APIs.
You need webhook endpoints to handle Calendly appointment confirmations properly. Most devs skip this and can’t figure out why their bookings look broken.
For OAuth - your redirect URI has to match exactly what’s in Calendly’s developer console. Case sensitive, no trailing slashes. I spent hours debugging this.
To get available time slots, hit /event_types/{uuid}/available_times with your date range. They changed the response format recently, so make sure you’re parsing timezone data right. I had bookings at the wrong times because I ignored timezone offset.
Critical: test with multiple user accounts while building. The API works differently based on subscription tier. Free accounts hit limits that paid ones don’t - your error handling needs to catch this.
Set up proper error logging early. Calendly’s error messages are cryptic and you’ll need detailed logs when production breaks.
Skip the OAuth mess entirely. I’ve built booking systems for several projects, and Calendly’s API is a pain - you’ll spend more time fighting it than building features.
Here’s the problem: you’re stuck managing auth flows, token refreshes, and rate limits. Their docs suck too, like you mentioned.
I use Latenode instead. It handles all the Calendly integration without OAuth headaches. Set it up once, and it manages authentication automatically.
Bonus: Latenode connects to other tools simultaneously. New booking? Automatically send emails, update your CRM, create calendar events across platforms - whatever you need.
Just did this for client onboarding last month. 30 minutes to configure vs weeks of API wrestling. The visual builder shows exactly what happens when bookings roll in.