MCP Server (AI Assistant Integration)

Charon ships a built-in Model Context Protocol (MCP) server that lets AI assistants — Claude, Cursor, GitHub Copilot, and others — read and write game data directly. The server communicates over stdio using the standard JSON-RPC MCP transport, so no network port is opened and no extra infrastructure is required.

With the MCP server running, an AI assistant can:

Discover and inspect schemas
Query, create, update, and delete game data documents
Import and export data in multiple formats
Generate typed source code (C#, TypeScript, Unreal C++, Haxe)
Manage localization (XLIFF / JSON round-trips)
Compare and patch game data between two sources

Prerequisites 

Install .NET 8 or later and the dotnet-charon tool:

dotnet tool install -g dotnet-charon

Verify the installation:

charon VERSION

Starting the MCP Server 

Run the MCP verb with no additional arguments:

charon MCP

The process stays running and communicates over stdin / stdout. Do not write anything else to stdout while the server is active — the transport is the raw MCP JSON-RPC stream and any extra output will corrupt the protocol.

All diagnostic logging should be going to a log file (see Logging below), so it never interferes with the transport.

Logging 

Because stdout is reserved for the MCP transport, use the --log option to write diagnostics to a file:

charon MCP --log /tmp/charon-mcp.log

Pass --verbose to include debug-level messages:

charon MCP --log /tmp/charon-mcp.log --verbose

Specifying --log con or --log out in MCP mode is silently ignored to protect the transport.

Configuring AI Clients 

Claude Desktop 

Add the following entry to your claude_desktop_config.json (usually at ~/Library/Application Support/Claude/claude_desktop_config.json on macOS or %APPDATA%\Claude\claude_desktop_config.json on Windows):

{
  "mcpServers": {
    "charon": {
      "command": "charon",
      "args": ["MCP"]
    }
  }
}

Restart Claude Desktop after editing the file.

Claude Code (CLI)

claude mcp add --transport stdio charon -- charon MCP

Cursor 

Open Settings → MCP → Add MCP Server and fill in:

Command: charon
Arguments: MCP

VS Code (GitHub Copilot)

Add to your workspace .vscode/mcp.json:

{
  "servers": {
    "charon": {
      "type": "stdio",
      "command": "charon",
      "args": ["MCP"]
    }
  }
}

Authentication for Remote Sources 

When a tool’s dataBase parameter points to a remote Charon service URL (e.g. https://charon.live/view/data/MyGame/main), set the CHARON_API_KEY environment variable before starting the server:

export CHARON_API_KEY=your_api_key_here
charon MCP

In client configuration files you can pass the variable directly:

{
  "mcpServers": {
    "charon": {
      "command": "charon",
      "args": ["MCP"],
      "env": {
        "CHARON_API_KEY": "your_api_key_here"
      }
    }
  }
}

Local file sources do not require an API key.

Data Sources 

Every tool accepts a dataBase parameter that identifies the game data source.

Local file — pass an absolute or relative path:

/home/user/project/gamedata.json
C:\Projects\MyGame\gamedata.gdjs
./data/gamedata.msgpack

Supported file extensions:

Format	Extensions
JSON	`.json`, `.gdjs`
MessagePack	`.msgpack`, `.msgpkg`, `.gdmp`
BSON	`.bson`, `.gdbs`
Gzip-compressed (any of the above)	`.json.gz`, `.gdjs.gz`, `.msgpack.gz`, etc.

Remote URL — pass the project URL from charon.live:

https://charon.live/view/data/RPG_Game/development

Remote sources require CHARON_API_KEY to be set. Unlike local files, remote connections are not pooled and are not reused between tool calls.

Available Tools 

Use the following command to inspect the MCP server:

npx @modelcontextprotocol/inspector charon MCP

Limitations and Remote-Only Use Case 

The built-in MCP server works with local files and with remote Charon service URLs that are reachable from the machine running the charon process. The game data file is loaded locally by the CLI tool.

If you need a fully-remote MCP setup where Charon itself runs as a cloud service and the CLI is not installed on the AI client’s machine, the MCP server cannot be used directly. As a fallback, charon.live exposes its full API through an OpenAPI 3 specification:

https://charon.live/api/v1/open.api.server.yml

AI clients that support OpenAPI-based tool use (such as those using function-calling from an OpenAPI schema) can configure that URL as an API tool source. Authentication is done with a bearer token equal to your CHARON_API_KEY value.