> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mcphub.app/llms.txt
> Use this file to discover all available pages before exploring further.

# MCP Apps

> Proxy interactive MCP Apps through single-server MCPHub routes

## Overview

MCPHub supports [MCP Apps](https://github.com/modelcontextprotocol/ext-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.

## 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

## 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.

## 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.

## 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.