Witcher 3 String Editor MCP

A local (stdio) MCP server for reading and editing The Witcher 3 .w3strings localization files — inspect entries, search text, translate or replace strings, add/delete entries, and save as version 162/163/164.

Every operation works on an in-memory document identified by a Guid handle; only save_document writes to disk, so you can edit a game file without touching the original.

Tools

Related MCP server: ue-bridge

Install

The package is a .NET tool, so clients launch it through dnx, which ships with the .NET 10 SDK. There is nothing to install globally and nothing to add to PATH — the first launch downloads the package from NuGet.org.

All configurations below launch the same stdio command:

dnx Witcher3StringEditor.MCP@0.1.0-beta.4 --yes

--yes skips the download confirmation prompt; @0.1.0-beta.4 pins the version, so upgrade by editing that number and restarting the client.

VS Code

Create .vscode/mcp.json in the workspace (or run MCP: Add Server from the Command Palette):

{
  "servers": {
    "w3strings": {
      "type": "stdio",
      "command": "dnx",
      "args": ["Witcher3StringEditor.MCP@0.1.0-beta.4", "--yes"]
    }
  }
}

Visual Studio

Create .mcp.json next to the .sln/.slnx. The servers block is identical to the VS Code one above; Visual Studio reads the same file format.

Cursor

Create .cursor/mcp.json in the project (or ~/.cursor/mcp.json for all projects). Cursor uses the mcpServers key:

{
  "mcpServers": {
    "w3strings": {
      "command": "dnx",
      "args": ["Witcher3StringEditor.MCP@0.1.0-beta.4", "--yes"]
    }
  }
}

Claude Code

claude mcp add w3strings -- dnx Witcher3StringEditor.MCP@0.1.0-beta.4 --yes

Claude Desktop

Edit %APPDATA%\Claude\claude_desktop_config.json (macOS: ~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "w3strings": {
      "command": "dnx",
      "args": ["Witcher3StringEditor.MCP@0.1.0-beta.4", "--yes"]
    }
  }
}

Restart Claude Desktop after editing the file.

Running from source

Before a release, or while developing, point the client at the project instead of the published package:

{
  "servers": {
    "w3strings-dev": {
      "type": "stdio",
      "command": "dotnet",
      "args": ["run", "--project", "Witcher3StringEditor.MCP/Witcher3StringEditor.MCP.csproj"]
    }
  }
}

Without the .NET 10 SDK

Publish the self-contained build and point command at the executable instead of dnx:

dotnet publish .\Witcher3StringEditor.MCP -c Release -r win-x64

{
  "servers": {
    "w3strings": {
      "type": "stdio",
      "command": "C:\\path\\to\\Witcher3StringEditor.MCP\\bin\\Release\\net10.0\\win-x64\\publish\\Witcher3StringEditor.MCP.exe"
    }
  }
}

Verify the connection

After restarting the client, the server should expose 15 tools (open_document … list_languages). If the client lists none, or every call fails with a generic message:

• Check that dnx resolves: dnx --help must work in a terminal (otherwise install the .NET 10 SDK).

• Check that the configured version actually exists on NuGet.org.

• Read the log — the client only shows a generic error, the real exception is always in %LOCALAPPDATA%\Witcher3StringEditor.MCP\logs\log<date>.txt (one file per day).

Build from source

dotnet run --project .\Witcher3StringEditor.MCP           # run from source
dotnet pack -c Release -r win-x64                        # build the win-x64 tool package

dotnet pack produces one platform-independent package plus one package per runtime identifier; all of them must be pushed to NuGet.org for dnx to resolve the right binary.

Notes

• .w3strings stores no readable key name, only an 8-digit uppercase hex hash; key names are empty after reopening a file.

• 163 is written as 162. Save with 164 for the Remastered edition, 162/163 for the classic and next-gen builds.

• Zero-hash key entries are dropped on save.

• The server has no undo: save to a new file when editing game content.

• Diagnostics go to the user's local application data, never to stdout and never to the working directory: %LOCALAPPDATA%\Witcher3StringEditor.MCP\logs\log<date>.txt on Windows and ~/.local/share/Witcher3StringEditor.MCP/logs/log<date>.txt on Unix-like systems. One file per day, with Serilog's default file retention of 31 files (1 GB per file).

License

Released under the MIT License.