CalendarPipe is a versatile calendar syncing tool that allows users to connect Google, Outlook, and Apple calendars through programmable 'pipes'. These pipes can be built visually or described in plain English with AI assistance. Users also have the option to write TypeScript for more complex operations. Events are sent as real invitations without requiring OAuth on the recipient side. Additionally, CalendarPipe provides an AI agent REST API, CalDAV support, and an MCP server for users who want to create their own calendars and send invites.