Cal.com is open-source scheduling software, an open-source alternative to Calendly, and its core job is booking meetings. It hands out shareable booking pages, manages availability across all of your connected calendars, and lets a prospect pick an open slot without any of the usual back and forth over email. Underneath the simple booking page sits a real system. You get round-robin and collective team scheduling, routing forms that send a lead to the right rep based on their answers, and workflows for reminders. The part that matters most to us is the open REST API, HMAC-signed webhooks, and the option to self-host the whole thing. In a GTM stack it sits at the inbound entry point. A booking is the first real intent signal a prospect gives you, and because Cal.com fires a webhook the moment it happens, that signal becomes the trigger for everything downstream instead of sitting in a silo. We reach for Cal.com on the inbound and post-meeting workflows we build. When a prospect books through the Cal.com link, Cal fires a webhook carrying the booking data, that data lands in Clay, and n8n routes it onward. The open API, webhooks, and self-hosting are exactly why we pick it over a closed scheduler.