Unicode support for non-latin language

[Sivan22]

Describe the bug
when sending or recieving a non-latin text, the text becomes Jibrish (Non-sense or ?????)

To Reproduce
send a request to one of the tools with non-latin characters

Expected behavior
it should handle all unicode-supported languages

Desktop (please complete the following information):

• OS: windows 11 home

[dsp-ant]

Do you have a repro? I am trying this and for me it works. What is your System encoding? Maybe it's releated to #123

[Richard-Weiss]

TL;DR:
I use

stdin.reconfigure(encoding='utf-8')
stdout.reconfigure(encoding='utf-8')

at the top of my server and encoding='utf-8' for file operations for example.

---

Have a similar issue in my Python MCP server for other unicode stuff, I added this line at the top of my server.py which fixes it:

stdout.reconfigure(encoding='utf-8')

With mitigation suggested in #112:

With my mitigation:

There's a different issue when it's unicode only, the message doesn't even hit my own server before erroring out from the SDK I believe:

Code is just this inside the tool:

path = arguments.path
content = arguments.content

await PathValidator.validate_file_path(path)
file_path = await PathValidator.resolve_absolute_path(path)

logger.debug(f"Writing content to {file_path}")
logger.debug(f"Content: {content}")
async with aiofiles.open(file_path, 'w') as f:
    await f.write(content)
logger.debug(f"Wrote content to {file_path}")

The mitigation in #112 fixes that particular issue, but I get the other encoding problem back, even with my own mitigation.
What did work for me is including encoding='utf-8' for file operations when using both mitigations, the debug log in the inspector won't decode it correctly though, but at least it works:

I'm on Windows 10 and SDK version 1.2.0 and using the lowlevel server.

[Sivan22]

thank you for that solution.
i've found another workaround using the environment variable PYTHONIOENCODING= "utf-8"

or using it in the mcp config :

{
  "mcpServers": {        
      "mcp_server": {
          "command": "uv",
          "args": [
              "--directory",
              "your/path/to/directory",
              "run",
              "mcp_server"
          ],
          "env": {
            "PYTHONIOENCODING": "utf-8" 
          }
      }
  }
}

this solution comes from modelcontextprotocol/servers#57

[Richard-Weiss]

Yeah, that's smart too. Claude suggested that, but I was unsure of where I could put the env variable because in the code would be too late for it to work.
Still need to include encoding='utf-8' when reading a file though.

Just noticed that it's actually better, because the MCP inspector output is then correct too.

[Kludex]

Is this still an issue?

[Richard-Weiss]

I can check in 9.5 hours or so. Is the "low-level" server implementation still a thing? I imagine the sdk has changed quite a lot in the past 7 months.

[Kludex]

It's still a thing, yep.

[Richard-Weiss]

Alright, I've updated that stone old server to use mcp 1.12.0 which just worked which was really nice, then I removed my own encoding handling, works well out of the box now 👍: