The only scheduling tool with a real app store
What sets Cal.com apart is that it's actually open. I integrated my product with their booking API (v2) and it was clean, well-documented, and simply worked — live availability and bookings behaved exactly as expected. Even better, they're the rare scheduling platform with a real, open app store: I was able to contribute my own integration as a pull request, and once a maintainer picked it up the review was fast and constructive. The open-source ethos isn't just marketing — you can read the code, build on it, and add to it. If you want scheduling you can extend rather than just rent, it's a great choice.