MCP Apps _meta.ui.resourceUri: what a Sume tool call shows

Nothing in the Sume code I read puts _meta.ui.resourceUri on a tool. tools/list returns a tools array and the server dispatches only initialize, ping, tools/list and tools/call. A host that supports MCP Apps therefore treats Sume tools as ordinary tools and shows their results as conversation content, not an iframe.

The MCP Apps facts are from the extension overview; the Sume facts from the server source and MCP tools and gates, read 2026-09-30.

What does an MCP App tool declare?

Per the overview, the tool description carries a _meta.ui.resourceUri field pointing to a ui:// resource, which the host can preload before the tool is called. The host then fetches that resource, an HTML page, and typically renders it in a sandboxed iframe. The resource's _meta.ui can include permissions and csp.

Where does Sume differ?

What will I see in an Apps-capable host?

The same thing as in any other client: the tools/call result. Generation tools return job data you read with jobs_wait and jobs_result, as in MCP tool call result structure. The finished artifact is a URL, so previewing it is something the host or you do after the result arrives.

Should I wait for Sume to ship an app UI?

Do not build around one. Nothing in the quickstart or the tools-and-gates page mentions it. Connect as usual with claude mcp add --transport http sume https://mcp.sume.com/mcp, keep idempotency_key on paid calls, and check the docs for changes.