Lessons from building 20 MCP Apps in 2 days (opens in new tab)

A few weeks back, my team sat down for two days and built around twenty MCP Apps. I came out with a much better idea of what they are, what they aren't (yet), and where the duct tape is currently holding things together. Here's the brain dump. If you haven't run into them yet: MCP Apps is the first official extension to the MCP spec. It lets a tool return a UI resource alongside its result. The host renders that UI inline as a sandboxed iframe. Tables, charts, forms, branded layouts, little i...