The document discusses how to build an agile marketing stack. It notes that the number of marketing tools has grown exponentially in recent years. It recommends selecting tools based on integration and connectivity to avoid a "stackapocalypse." Specifically, it suggests using tools like Segment, Clearbit, Autopilot, Salesforce, and Amplitude that easily integrate and connect different marketing functions. It also highlights how RealThread was able to reinvent its stack without code by implementing tools like these into its new, integrated stack.