Claude shows "Could not attach to MCP server fetch"

[sean-lynch]

Taking the new fetch server for a spin and having some difficulty loading it locally.

My claude_desktop_config.json is below.

{
  "mcpServers": {
    "puppeteer": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-puppeteer"]
    },
    "fetch": {
      "command": "/Users/sean/.local/bin/uvx",
      "args": ["mcp-server-fetch"]
    }
  }
}

Needed to provide absolute path to uvx. Without that, I get a separate "Could not connect to MCP server fetch". I'm assuming that's a function of how I have it installed so not worried about that.

Connecting via the inspector doesn't seem to have any issues:

npx -y @modelcontextprotocol/inspector uvx mcp-server-fetch

Is there any logging in Claude Desktop I can enable to provide more details on the error?

[jspahrsummers]

Very odd! Can you try the debugging steps here and see if that reveals any information?

[davepeckjr]

I'm having the same issue, this is what I'm getting:

2024-11-25T21:14:11.495Z [error] Error in MCP connection to server fetch: Error: spawn uvx ENOENT
at ChildProcess._handle.onexit (node:internal/child_process:286:19)
at onErrorNT (node:internal/child_process:484:16)
at process.processTicksAndRejections (node:internal/process/task_queues:82:21) {
errno: -2,
code: 'ENOENT',
syscall: 'spawn uvx',
path: 'uvx',
spawnargs: [Array]
}
2024-11-25T21:14:11.495Z [error] Could not start MCP server fetch: Error: spawn uvx ENOENT
at ChildProcess._handle.onexit (node:internal/child_process:286:19)
at onErrorNT (node:internal/child_process:484:16)
at process.processTicksAndRejections (node:internal/process/task_queues:82:21) {
errno: -2,
code: 'ENOENT',
syscall: 'spawn uvx',
path: 'uvx',
spawnargs: [Array]
}

[sean-lynch]

@jspahrsummers thanks for the pointer! That showed me the exact problem:

Because the current Python version (3.9.6) does not satisfy Python>=3.10

@davepeckjr - The error you are seeing was the same one I had when I saw the slightly different "Could not connect to MCP server fetch", and I had to put in the absolute path into my config. Are you seeing the error say connect or attach in your error?

[zhaolongzhong]

I also had the same issue that needed a full path for uvx, it could be an issue related to how you install uv. The following works for me,
brew install uv

Make sure,

~$ which upx
/opt/homebrew/bin/upx
~$ which uvx
/opt/homebrew/bin/uvx
~$ 

[sean-lynch]

Yep, I had to hardcode both my uvx path and my python interpreter path into the config (using which to figure out both).

{
  "mcpServers": {
    "fetch": {
      "command": "/path/to/uvx",
      "args": ["--python", "/path/to/python", "mcp-server-fetch"]
    }
  }
}