mcp-server-motherduck 0.7.1: can only concatenate str (not "_duckdb._sqltypes.DuckDBPyType") to str

TL;DR

The fix was released as 0.7.2 the same day. If youre stuck on 0.7.1, pin the working version in your MCP config until you can upgrade: `json { "mcpServers": { "motherduck": { "command": "uvx", "args": ["mcp-server-motherduck@0.7.0"] } } } ` That pin worked for the reporter.

Steps

1. After upgrading to mcp-server-motherduck 0.7.1, every query failed with Error executing query: can only concatenate str (not "_duckdb._sqltypes.DuckDBPyType") to str. Even SELECT 1 broke. The previous version worked fine, and it showed up when used through the Continue VS Code extension.
2. A regression in the 0.7.1 release: the maintainer admitted he had tested the wrong version before shipping. The fix was released as 0.7.2 the same day.
3. If youre stuck on 0.7.1, pin the working version in your MCP config until you can upgrade:

{
 "mcpServers": {
 "motherduck": {
 "command": "uvx",
 "args": ["mcp-server-motherduck@0.7.0"]
 }
 }
}

4. That pin worked for the reporter. Then upgrade to 0.7.2+ for the real fix.

When to use

You are seeing this: After upgrading to mcp-server-motherduck 0.7.1, every query failed with Error executing query: can only concatenate str (not "\duckdb.\sqltypes.DuckDBPyType") to str. Use this skill when you run into "mcp-server-motherduck 0.7.1: can only concatenate str (not "duckdb.sqltypes.DuckDBPyType") to str".

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 0.7.1, as 0.7.2, mcp-server-motherduck 0.7.0. 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/39

Someone asked: After upgrading to mcp-server-motherduck 0.7.1, every query failed with Error executing query: can only concatenate str (not "_duckdb._sqltypes.DuckDBPyType") to str. Even SELECT 1 broke. The previous version worked fine, and it showed up when used through the Continue VS Code extension. The verified resolution: A regression in the 0.7.1 release: the maintainer admitted he had tested the wrong version before shipping. The fix was released as 0.7.2 the same day.

If youre stuck on 0.7.1, pin the working version in your MCP config until you can upgrade:

{
  "mcpServers": {
    "motherduck": {
      "command": "uvx",
      "args": ["mcp-server-motherduck@0.7.0"]
    }
  }
}

That pin worked for the reporter. Then upgrade to 0.7.2+ for the real fix. Thread: https://vectle.com/threads/thr_G5lKvO7dchR8zPvV5wA8Rw