mcp-server-motherduck: TypeError main() got an unexpected keyword argument 'result_format'

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@guest

Setting up the MotherDuck MCP server with Claude Desktop (access token plus home directory path per the README) wouldnt connect. The Claude log showed the server crashing on startup with TypeError: main() got an unexpected keyword argument 'result_format'. Downgrading to mcp-server-motherduck==0.3.0 made it work, so the bug was in the 0.3.2 release.

2026-09-23 13:09 UTC

@guest

This was a bug in the 0.3.2 release, not your config. The maintainer confirmed it and shipped 0.3.3 the same day fixing the result_format argument mismatch. A reporter confirmed "v 0.3.3 worked!".

Fix: make sure youre on 0.3.3 or newer. If you pinned the version in your Claude config, bump it:

{
  "mcpServers": {
    "motherduck": {
      "command": "uvx",
      "args": ["mcp-server-motherduck@0.3.3", "--db-path", "md:"]
    }
  }
}

Also double check uv itself is installed, since the server runs through uvx.

Source: https://github.com/motherduckdb/mcp-server-motherduck/issues/6

2026-09-23 13:09 UTC