Claude Desktop Configuration¶

This guide explains how to configure Claude Desktop to use the RIDDL MCP Server for AI-assisted domain modeling.

Prerequisites¶

Claude Desktop application installed
riddlg installed and on your PATH (see Installation):
```
brew install ossuminc/tap/riddlg
```

Configuration¶

Claude Desktop launches MCP servers as local processes (stdio transport) via a JSON configuration file.

Configuration File Location¶

Platform	Path
macOS	`~/Library/Application Support/Claude/claude_desktop_config.json`
Windows	`%APPDATA%\Claude\claude_desktop_config.json`
Linux	`~/.config/Claude/claude_desktop_config.json`

Adding the RIDDL MCP Server¶

Edit your configuration file to add the RIDDL server:

{
  "mcpServers": {
    "riddl": {
      "command": "riddlg",
      "args": ["mcp"]
    }
  }
}

That's the whole setup — no URL, no API key. Claude Desktop starts riddlg mcp for you when it launches.

Complete Example¶

If you have other MCP servers configured, add RIDDL alongside them:

{
  "mcpServers": {
    "riddl": {
      "command": "riddlg",
      "args": ["mcp"]
    },
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/path/to/files"]
    }
  }
}

riddlg must be found on PATH

Claude Desktop does not run your shell profile, so if riddlg isn't on the system PATH it may not be found. Use the absolute path (e.g. /opt/homebrew/bin/riddlg) as the command if the tools don't appear.

Restart Claude Desktop¶

After modifying the configuration:

Quit Claude Desktop completely
Relaunch Claude Desktop
The RIDDL tools should now be available

Verify Connection¶

Ask Claude to validate some RIDDL:

"Can you validate this RIDDL code for me?"
domain Example is { ??? }

Claude should use the riddl_validate tool and return validation results.

Usage Examples¶

Validate RIDDL Code¶

"Please validate this RIDDL model and explain any errors:"

domain OrderManagement is {
  context Orders is {
    entity Order is { ??? }
  }
}

Check Completeness¶

"Analyze this model for completeness and tell me what's missing:"
domain Inventory is {
  context Warehouse is {
    type ProductId is Id(Product)
  }
}

Convert Natural Language¶

"I need to model an e-commerce system with shopping carts, orders, and inventory tracking. What RIDDL structure would you suggest?"

Explain Errors¶

"I got this error: 'Undefined reference to type CustomerID'. What does this mean and how do I fix it?"

Available RIDDL Tools¶

Once connected, Claude can use all of the RIDDL MCP tools — for example:

Tool	Ask Claude to...
`riddl_validate`	"Validate this RIDDL code"
`riddl_outline`	"Outline the definitions in this model"
`validate-partial`	"Check this incomplete model"
`check-completeness`	"What's missing from this model?"
`check-simulability`	"Can this model be simulated?"
`map-domain-to-riddl`	"Convert this description to RIDDL"
`explain-error`	"Explain this error message"
`suggest-next`	"What should I add next?"

See MCP Tools for the full catalog of 13.

Troubleshooting¶

Tools Not Appearing¶

Restart Claude Desktop after configuration changes
Check for JSON syntax errors in the configuration file
Verify riddlg runs from a terminal: riddlg mcp should start and wait for input (press Ctrl+C to exit)
If riddlg isn't found, use its absolute path as the command

Verifying riddlg Itself¶

riddlg version
riddlg validate model.riddl

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