I’ve been playing around with Pencil along with Paper, both newer agentic design tools. The multi-agent demo is genuinely impressive—six AI agents designing an app simultaneously, each with its own cursor, name, and chat on the canvas.
Tom Krcha, Pencil’s CEO, speaking on Peter Yang’s channel, on the format bet at the center of the product:
It’s generating basically a descriptor for the design. And then what you can do, you can essentially ask it what kind of code you want to convert it into. Because we wanted to make sure that it’s sort of platform agnostic. […] So we have this platform agnostic file format. We call it .pen. It’s essentially just JSON-based format. We wanted to really build this format to be agentic from the ground up.
Krcha frames it as “agentic PDF.” I could get behind platform agnosticism as a philosophy, but I need more convincing. The .pen format is still a translation layer between the design and the code. That means migration from Figma, especially for teams with established design systems. And I’m skeptical that a button in Pencil’s built-in design system will correctly map to the right reusable code component when the agent translates .pen to production code. I need to test it out more for myself.
We have enterprises using that for this specific purpose, to convert their design systems into pen format and make sure that it lives in the Git. This is the source of truth for everybody now.
“Source of truth” is doing heavy lifting in that sentence. For teams with mature design systems, the source of truth is the code component, not a JSON representation of it.
This is a pretty impressive demo nonetheless, and it’s a moment of delight to give agents a name and a “face” if you will. Krcha:
Those cursors, it seems like a small touch, but it’s the first time I have seen AI humanized. It feels like there’s someone there. It’s crazy, it’s just a cursor.
I Watched 6 AI Agents Design an App Together And It Blew My Mind | Tom Krcha
Tom is the CEO of Pencil, one of the coolest AI design tools that I’ve ever tried. Watching 6 AI agents design a beautiful app in real-time will genuinely blow your mind. Tom showed me how it all works under the hood (a simple JSON file?!) and how you can use Pencil to design right where you code…





















