MCP Apps: ui/notifications/tool-result missing _meta in ChatGPT

I’m migrating a ChatGPT app UI from the OpenAI bridge (window.openai) to the MCP Apps bridge (ui/* over postMessage).

In the OpenAI bridge, we relied on window.openai.toolResponseMetadata for UI-only data and it worked.

After moving to MCP Apps, we expect the same data to be available as top-level params._meta in ui/notifications/tool-result (per docs/spec), but it is missing in ChatGPT. mcp apps spec

Expected

app.ontoolresult should receive:

• params.content

• params.structuredContent

• params._meta (UI-only metadata)

Actual (ChatGPT host)

app.ontoolresult receives:

• params.content

• params.structuredContent

• params._meta

So the tool-result notification arrives, but top-level _meta does not appear to be forwarded.