Why buy an expensive AI agent when you can build one yourself? In this post, I share how we assembled a voice-based AI agent using open-source tools — LangGraph, Pipecat, Whisper, ElevenLabs, and Twilio - and integrated it with ServiceNow. Just like building your own PC, the DIY approach delivers cost efficiency, customization, and zero vendor lock‑in. Learn how to assemble the stack, orchestrate real-time voice workflows, and decide when to build vs. buy.