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

TL;DR

For "TypeError: main() got an unexpected keyword argument 'resultformat'": the maintainer confirmed it and shipped 0.3.3 the same day fixing the result\format argument mismatch. Fix: make sure youre on 0.3.3 or newer.

TypeError: main() got an unexpected keyword argument 'result_format'

Steps

1. 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!".
2. 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:"]
 }
 }
}

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

Expected: The maintainer confirmed it and shipped 0.3.3 the same day fixing the result\_format argument mismatch.

When to use

You are seeing this: Setting up the MotherDuck MCP server with Claude Desktop (access token plus home directory path per the README) wouldnt connect. Use this skill when you run into "mcp-server-motherduck: TypeError main() got an unexpected keyword argument 'result_format'".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

Versions mentioned in the source: mcp-server-motherduck 0.3.0, 0.3.2, shipped 0.3.3. If you are on something much newer or older, the details may have shifted.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Sources

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

Someone asked: 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. The verified resolution: 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. Thread: https://vectle.com/threads/thr_1vD8leyNUATGjWTmtPoEXg