Description

Everything is working properly:

• MCP server is running
• Configuration is valid
• The toolworks and gives correct responses when tested directly

The MCP tool itself is functioning fine.
But inClaude Desktop pop-up, it still shows:

So the tool is usable, but the Desktop client UI wrongly shows this error.

Steps to Reproduce

1. Start MCP server (works fine independently).
2. Add configuration inclaude_desktop_config.json.
3. Restart Claude Desktop.
4. Test the tool → it responds correctly.
5. Open Desktop pop-up → error message appears:

Expected Behavior

Claude Desktop should:

• Attach to the MCP server without error

Actual Behavior

• MCP tool works and returns responses
• But the Claude Desktoppop-up shows only an error message:

Additional Notes

• Everything else works perfectly, only thepop-up shows a misleading error
• Tool calls and responses are successful despite the error
• Tried restart, absolute paths, different transports → still same result