MCP Just Got a Native App Platform — Its Default CSP Blocks Everything MCP Apps is the first official extension folded directly into the Model Context Protocol's stable core spec: a tool can now declare an interactive HTML UI — a ui:// resource — that a host renders in a sandboxed iframe instead of just dumping text back to the model. Think a dashboard, a form, a live chart, embedded right in the conversation. It's a genuinely useful capability, and it's also brand new enough that almost n...