The call for an agentic standard: We need to stop shipping the same form four different times

The useful part

Every assistant draws its own way, and the bill lands on the people who already maintain your button component. Connecting was the easy part and the plumbing is close to settled for MCP Servers, which followed the lead of HTTP dressed up for the AI era. What isn't is what each client does when your agent needs a date picker on screen: which components exist, who owns the rendering, what it looks like when it shows up on a screen.

How it works

• It matters because it is the one proposal on the table that no vendor "owns." Working this out should not be a research project, and this is a call to arms to get there.
• There are four ways a client can do it, and every product you care about sits in one of them.
• Nobody publishes that comparison, so sorting out which client does which took four specifications, a protocol proposal and a Google engineering post, and none of them agree on what to call any of it.
• Introduced in December 2025, it is declarative: the agent sends JSON naming components the client already holds in a catalog, and the client draws them in its own code.
• Version 1.0 is still a release candidate and it looks a lot like the HTML constructs of 1999.

What to take from it

A2UI Declarative JSON, rendered by the client The agent names components the client already holds, and nobody owns the vocabulary.

Details worth keeping

Google's trying to create that standard — A2UI. It's short for agent-to-UI, their attempt at a shared approach i.e. No markup crosses the wire, and no styling either.