MCP Apps vs OpenAI Apps SDK: are they competing standards?

If you have started building tools for AI chat hosts, you have probably hit the same fork in the road. There are two ways to add a user interface to a tool right now. The first is MCP Apps, the open standard from the Model Context Protocol. The second is the OpenAI Apps SDK, the framework OpenAI shipped for the ChatGPT app store. They both let your tool render a UI inside the chat. They both run inside a sandboxed iframe. They both talk to your server over JSON-RPC. So the question almost every...