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IntelliJ AI Assistant Configuration

This guide explains how to configure IntelliJ IDEA's built-in AI Assistant to use the RIDDL MCP Server for AI-assisted domain modeling.

Prerequisites

  • IntelliJ IDEA with the AI Assistant plugin (MCP support requires a recent version — 2025.1 or later)
  • AI Assistant enabled in your JetBrains account
  • riddlg installed and on your PATH (see Installation): 
    brew install ossuminc/tap/riddlg

Configuration

JetBrains AI Assistant launches MCP servers as local processes (stdio transport).

Settings UI Method

  1. Open Settings (Cmd+, or Ctrl+Alt+S)
  2. Navigate to Tools > AI Assistant > Model Context Protocol (MCP)
  3. Click Add (+) and configure the server:
Field Value
Name riddl
Command riddlg
Arguments mcp
  1. Apply and let the IDE start the server.

JSON Method

Some versions let you paste a server definition as JSON. The RIDDL server uses the standard stdio form (the same shape Claude Desktop uses):

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

No URL and no API key are involved. If riddlg isn't on the system PATH, use its absolute path as the command.

Restart IntelliJ

After configuring:

  1. Close IntelliJ IDEA completely
  2. Relaunch IntelliJ IDEA
  3. Open a RIDDL file to verify the tools are available

Verify Connection

Open the AI Assistant chat and ask:

Can you validate this RIDDL code? 

domain Example is { ??? }

The AI should use the riddl_validate tool and return validation results.

Using with the RIDDL Plugin

For the best experience, install both:

  • RIDDL4IDEA Plugin - Syntax highlighting, inline error markers, and local validation
  • AI Assistant with the RIDDL MCP server - Natural-language queries, code generation, error explanations, and completeness analysis

Usage Examples

Validate the Open File

With a .riddl file open in the editor:

Validate this RIDDL file and explain any errors

Generate RIDDL Code

Create a RIDDL entity for managing user accounts with login history and password reset functionality

Understand Errors

The RIDDL plugin shows "Undefined reference to type PaymentMethod" - what does this mean and how do I fix it?

Check Completeness

Is this domain model complete enough to generate a working application?

Troubleshooting

AI Assistant Not Available

  • Verify the AI Assistant plugin is installed and enabled
  • Check your JetBrains account has AI features enabled
  • Update to a version with MCP support (2025.1+)

MCP Tools Not Working

  • Restart IntelliJ after configuration changes
  • Verify riddlg mcp starts from a terminal (it waits on stdin)
  • If riddlg isn't found, use its absolute path as the command
  • Check Help > Show Log in Finder/Explorer for errors

Available RIDDL Tools

Tool Use For
riddl_validate Check RIDDL source for errors
riddl_outline Summarize a model's definitions
validate-partial Check incomplete models
check-completeness Find missing elements
check-simulability Verify simulation readiness
map-domain-to-riddl Convert descriptions to RIDDL
explain-error Understand validation errors
suggest-next Get recommendations

See MCP Tools for the full catalog of 13.

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