LPC MCP Server

Bring LPC development into 2025 with AI-powered code intelligence.

This MCP (Model Context Protocol) server wraps the jlchmura/lpc-language-server and exposes it to AI assistants, enabling natural language queries about your LPC codebase with real language server-powered understanding.

What This Enables

AI assistants can now:

• Understand your LPC code structure through the language server
• Get real documentation from hover information
• Jump to definitions and find references
• Answer natural language questions about your mudlib
• Trace inheritance chains and function calls
• Explain complex code patterns

All through conversation, powered by actual code intelligence instead of pattern matching.

Features

• lpc_hover: Get documentation/hover information for symbols
• lpc_definition: Jump to definition of symbols
• lpc_references: Find all references to a symbol
• lpc_diagnostics: Get real-time errors, warnings, and hints from the language server
• Workspace-aware: Reads your lpc-config.json for proper symbol resolution
• Fast: Direct JSON-RPC communication with the language server

Prerequisites

1. Install Node.js

Node.js 20+ required:

node --version  # Should be v20.0.0 or higher

2. Install the LPC Language Server Extension

The extension must be installed in VS Code (the server binary is bundled with it):

code --install-extension jlchmura.lpc

Verify installation:

ls ~/.vscode/extensions/jlchmura.lpc-*/out/server/src/server.js

3. Install Dependencies

cd /path/to/lpc-mcp
npm install

4. Create lpc-config.json in Your Mudlib

The language server needs this config file at your mudlib root to understand includes, simul_efuns, etc.

Example /path/to/your/mudlib/lpc-config.json:

{
  "driver": {
    "type": "fluffos"
  },
  "libFiles": {
    "master": "adm/obj/master.c",
    "simul_efun": "adm/obj/simul_efun.c",
    "global_include": "include/global.h"
  },
  "libInclude": [
    "include",
    "include/driver",
    "adm/include"
  ],
  "exclude": [
    ".git/",
    "tmp/"
  ]
}

Setup for Different AI Tools

Warp (Terminal)

Add to your Warp MCP configuration:

Location: Settings → AI → Model Context Protocol

{
  "lpc": {
    "command": "node",
    "args": ["/absolute/path/to/lpc-mcp/index.js"],
    "env": {
      "LPC_WORKSPACE_ROOT": "/path/to/your/mudlib"
    }
  }
}

Important: Use absolute paths! Replace:

• /absolute/path/to/lpc-mcp/index.js with the actual path to this repo
• /path/to/your/mudlib with the directory containing your lpc-config.json

Restart Warp after adding the configuration.

Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json (macOS) or equivalent:

{
  "mcpServers": {
    "lpc": {
      "command": "node",
      "args": ["/absolute/path/to/lpc-mcp/index.js"],
      "env": {
        "LPC_WORKSPACE_ROOT": "/path/to/your/mudlib"
      }
    }
  }
}

Restart Claude Desktop after configuration.

Cline (VS Code Extension)

Add to your Cline MCP settings:

{
  "mcpServers": {
    "lpc": {
      "command": "node",
      "args": ["/absolute/path/to/lpc-mcp/index.js"],
      "env": {
        "LPC_WORKSPACE_ROOT": "/path/to/your/mudlib"
      }
    }
  }
}

GitHub Copilot (VS Code)

Prerequisites:

• Install the Copilot MCP extension: code --install-extension automatalabs.copilot-mcp

Configuration: Add to ~/Library/Application Support/Code/User/mcp.json (macOS) or equivalent:

{
  "servers": {
    "lpc": {
      "type": "node",
      "command": "node",
      "args": ["/absolute/path/to/lpc-mcp/index.js"],
      "env": {
        "LPC_WORKSPACE_ROOT": "/path/to/your/mudlib"
      }
    }
  },
  "inputs": []
}

Other MCP-Compatible Tools

The configuration is the same for any MCP-compatible tool:

1. Add the server to your MCP configuration
2. Provide the Node.js command and path to index.js
3. Set LPC_WORKSPACE_ROOT environment variable to your mudlib root

Optional environment variables (LPC_DEBUG, LPC_LSP_PATH) can be added to the env block in the same way. See the Environment Variables section for the full list.

Usage Examples

Once configured, you can ask your AI assistant natural language questions:

"What does the query_short() function do in room.c?" → AI uses lpc_hover to get documentation

"Where is STD_OBJECT defined?" → AI uses lpc_definition to find the file

"Find all places that call set_room_size()" → AI uses lpc_references to locate all callers

"Explain how the maze generation algorithm works" → AI reads code and uses hover info to understand functions

"What's the inheritance tree for rooms?" → AI traces inherit statements and jumps to definitions

"Check if this LPC file has any syntax errors" → AI uses lpc_diagnostics to validate the code

"Why won't this LPC code compile?" → AI checks diagnostics for errors like undeclared variables or type mismatches

Testing

To verify the server works:

# Set workspace root for testing
export LPC_WORKSPACE_ROOT=/path/to/your/mudlib

# Start the server (it will wait for MCP protocol messages)
node index.js

The server should output:

Starting LPC Language Server...
Initializing LSP...
LPC Language Server started successfully
LPC MCP Server running on stdio

Troubleshooting

Server won't start

Check the LPC extension is installed:

code --list-extensions | grep jlchmura.lpc

Check logs (for Warp):

tail -f ~/.local/state/warp-terminal/mcp/*.log

Language server not resolving symbols

Verify workspace root:

• Make sure LPC_WORKSPACE_ROOT points to the directory with lpc-config.json
• Use absolute paths, not relative

Check your lpc-config.json:

cat $LPC_WORKSPACE_ROOT/lpc-config.json

Extension version mismatch

If the extension path doesn't match, update line 40 in index.js:

const lspPath = path.join(
  process.env.HOME,
  ".vscode/extensions/jlchmura.lpc-VERSION/out/server/src/server.js"
);

Find your version:

ls ~/.vscode/extensions/ | grep jlchmura.lpc

Environment Variables

| Variable | Required | Description | | --- | --- | --- | | LPC_WORKSPACE_ROOT | Yes | Absolute path to your mudlib root (the directory containing lpc-config.json) | | LPC_DEBUG | No | Set to true or 1 to enable debug mode, which loads a local development build of the LPC language server instead of the installed VS Code extension | | LPC_LSP_PATH | No | Absolute path to a custom server.js for the LPC language server. Only used when LPC_DEBUG is enabled. If not set, debug mode falls back to out/server/src/server.js relative to process.cwd() |

Debug Mode Example

Shell / terminal:

# Use a local checkout of the LPC language server
export LPC_DEBUG=true
export LPC_LSP_PATH=/path/to/lpc-language-server/out/server/src/server.js
export LPC_WORKSPACE_ROOT=/path/to/your/mudlib
node index.js

MCP config file (.mcp.json, claude_desktop_config.json, etc.):

{
  "mcpServers": {
    "lpc": {
      "command": "node",
      "args": ["/absolute/path/to/lpc-mcp/index.js"],
      "env": {
        "LPC_WORKSPACE_ROOT": "/path/to/your/mudlib",
        "LPC_DEBUG": "true",
        "LPC_LSP_PATH": "/path/to/lpc-language-server/out/server/src/server.js"
      }
    }
  }
}

How It Works

AI Assistant
    ↓ (natural language)
  MCP Protocol
    ↓ (tool calls: lpc_hover, lpc_definition, lpc_references)
  This Server
    ↓ (JSON-RPC: textDocument/hover, etc.)
  LPC Language Server
    ↓ (parses LPC, reads lpc-config.json)
  Your Mudlib

1. AI assistant sends MCP tool requests
2. Server reads the file and sends textDocument/didOpen to LSP
3. Server translates MCP → LSP JSON-RPC requests
4. LSP analyzes code using your lpc-config.json
5. Server returns LSP response as MCP result
6. AI understands your code structure!

Credits

• John (jlchmura) - The INCOMPARABLY SKILLED MASTER PROGRAMMER whose LPC language server rescued LPC development from 1995. Without his greatness, kindness, and all-around hunk demeanour, we would still be grep-ing through mudlibs like cavemen. This MCP server is merely a humble wrapper around his genius.
• Model Context Protocol - The protocol making this possible
• Built in an hour of inspired hacking in 2025

License

@gesslar/lpc-mcp is released under the 0BSD.

This package includes or depends on third-party components under their own licenses:

| Dependency | License | | --- | --- | | @gesslar/toolkit | 0BSD | | @gesslar/uglier | 0BSD | | @modelcontextprotocol/sdk | MIT | | vscode-jsonrpc | MIT | | zod | MIT |

Note

The LPC language server itself (jlchmura/lpc-language-server) is under its own license.