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Overview

MCPHub supports MCP Apps as a transparent proxy. It forwards UI-linked tool metadata, app-only tools, ui:// resources, and upstream list-change notifications. MCPHub does not render app UIs in its dashboard. No MCPHub configuration switch is required. Support is enabled automatically when the downstream host advertises the io.modelcontextprotocol/ui extension with the text/html;profile=mcp-app MIME type.

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Routing Requirements

MCP Apps passthrough is enabled only when a request route resolves to exactly one connected MCP upstream server:
  • /mcp/{server}
  • /mcp/{group} when the group contains one visible MCP server
  • /mcp when only one MCP server is visible to the caller
Aggregate routes and $smart routes continue to work as ordinary MCP routes. On those routes MCPHub:
  • hides app-only tools such as tools with _meta.ui.visibility: ["app"]
  • removes Apps-specific _meta.ui and legacy _meta["ui/resourceUri"] fields
  • rejects direct calls to app-only tools
  • rejects unlisted ui:// resource reads

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Tool Names

Ordinary MCPHub routes expose qualified tool names such as weather::forecast, using your configured name separator. An eligible MCP Apps route exposes the upstream tool names unchanged, such as forecast. This allows calls from the app iframe to pass through without rewriting. Qualified aliases remain accepted for compatibility.

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UI Resources

MCP Apps servers may omit UI-only resources from resources/list. On an eligible Apps route, MCPHub forwards direct resources/read calls for unlisted ui:// URIs to the single upstream server. Ordinary listed resources remain readable, but Apps-specific metadata is removed outside eligible Apps routes.

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Dynamic Lists

MCPHub subscribes to upstream tools/list_changed, resources/list_changed, and prompts/list_changed notifications. It refreshes its cache, updates Smart Routing embeddings for model-visible tools, and notifies connected downstream clients.