[FEATURE] MCP capability advertising is missing (MCP Apps).

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

MCP Apps support has recently been introduced to Claude Desktop. However, the implementation seems incomplete.

More specifically, Claude Desktop does not advertise its MCP Apps capability to the MCP servers it connects to, even though it should. In fact, after some testing, it seems like Claude Desktop does not advertise any capability.

This essentially prevents MCP Servers from performing Graceful Degradation for clients that do not support MCP Apps, which requires knowing whether they should expose UI-enabled versions of the tools or only expose text-only tools.

Proposed Solution

Claude Desktop should advertise its MCP Apps support according to the MCP Apps specification.

Alternative Solutions

There are currently no workarounds to this. MCP Servers that check the client capabilities will believe that Claude Desktop does NOT support MCP Apps.

Priority

Critical - Blocking my work

Feature Category

MCP server integration

Use Case Example

Here is a concrete example of why this is needed:

• The MCP App will describe the tool with "This tool displays a UI that contains the info to the user", therefore the LLM will not write the output in plain text, instead it will just say "here is a UI with your info!".
• In case MCP apps are not supported, the UI will not be displayed, but the LLM will still go "here is a UI with your info!" and leave the user with no info.
• To remedy this, the description of the tool needs to be dynamically updated to "This tool returns the info, format and expose it to the user." for clients that do not support MCP Apps, the LLM will then output the information to the user.
• This requires that clients advertise their capabilities properly.

Additional Context

_No response_