Fixes › Claude Desktop

MCP server not showing in Claude Desktop

Claude Desktop

The error

No hammer/tools icon appears, or "Could not attach to MCP server" / "MCP server failed" in Claude Desktop

Why it happens

Claude Desktop reads claude_desktop_config.json only at startup. Editing the wrong file, invalid JSON, or not fully quitting the app (it keeps running in the tray/menu bar) are the usual causes.

How to fix it

  1. Edit the right file
    macOS: ~/Library/Application Support/Claude/claude_desktop_config.json. Windows: %APPDATA%\Claude\claude_desktop_config.json. Easiest path: Settings → Developer → Edit Config.
    {
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/Users/you/Desktop"]
    }
  }
}
  2. Fully quit and restart
    Quit from the menu bar/tray (Cmd+Q on macOS), not just close the window, then reopen.
  3. Read the logs
    macOS: ~/Library/Logs/Claude/mcp*.log. Windows: %APPDATA%\Claude\logs\.
    tail -n 50 -f ~/Library/Logs/Claude/mcp*.log
  4. Use absolute paths
    Paths in args (folders, scripts) must be absolute; ~ and relative paths are not expanded.

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Sources