ag-ui-protocol/ag-ui ? reverse-engineered prompt

I want to build a system for connecting AI agents to user interfaces. Think of it as an open protocol that standardizes how agents running on a server can talk to a frontend web app. It should be event-based to allow for things like real-time chat streaming.

I want agents to be able to do more than just send text; they should be able to render generative UI elements directly in the app, like forms or buttons. A key feature is making sure the agent and the UI are always in sync with each other's state, and allowing for a "human-in-the-loop" workflow where the user can collaborate with the agent. It's really important that this system is flexible and can integrate with popular agent frameworks like LangGraph, CrewAI, and LlamaIndex. Build out the core protocol, some SDKs for different frameworks, and example apps.