CodeQL LSP MCP Server

A Model Context Protocol (MCP) server that wraps the CodeQL Language Server Protocol (LSP) to enable LLM agents to write CodeQL queries with intelligent code completion, hover information, and other language features. This server reuses key concepts from the VS Code CodeQL extension to provide a robust language server interface. This is different from a MCP server that wraps the CodeQL CLI tool. However, you can also add CodeQL CLI commands to the server too. Feel free to contribute.

• Installation
• Tools
• Citation

Installation

1. Prerequisites

• CodeQL CLI installed and available in PATH or set CODEQL_PATH environment variable
• Node.js 18 or later

2. Build

cd codeql-lsp-mcp 
npm install
npm run build

3. Add MCP Configuration

Add to your MCP client configuration:

 {
    "mcpServers": {
      "codeql": {
        "command": "node",
        "args": ["/path/to/codeql-lsp-mcp/dist/index.js"] 
      }
    }
  }

[mcp_servers.codeql]
command = "node"
args = ["/path/to/codeql-lsp-mcp/dist/index.js"]

Logging

If you would like to enable logging, in the LSP client you can set this.verbose = true;.

Tools

1. codeql_open_file

Open a CodeQL file in the language server.

{
  "tool": "codeql_open_file",
  "arguments": {
    "file_uri": "file:///workspace/query.ql",
    "content": "import javascript\n\nfrom Function f\nwhere f.getName() = \"eval\"\nselect f"
  }
}

2. codeql_complete

Get code completions at a specific position.

{
  "tool": "codeql_complete",
  "arguments": {
    "file_uri": "file:///workspace/query.ql",
    "line": 2,
    "character": 5,
    "trigger_character": "."
  }
}

3. codeql_hover

Get hover information (documentation) at a position.

{
  "tool": "codeql_hover",
  "arguments": {
    "file_uri": "file:///workspace/query.ql",
    "line": 1,
    "character": 7
  }
}

4. codeql_definition

Go to definition for a symbol.

{
  "tool": "codeql_definition",
  "arguments": {
    "file_uri": "file:///workspace/query.ql",
    "line": 3,
    "character": 10
  }
}

5. codeql_diagnostics

Get diagnostics (errors, warnings) for a file.

{
  "tool": "codeql_diagnostics",
  "arguments": {
    "file_uri": "file:///workspace/query.ql"
  }
}

6. codeql_format

Format a CodeQL file or selection.

{
  "tool": "codeql_format",
  "arguments": {
    "file_uri": "file:///workspace/query.ql",
    "range": {
      "start": { "line": 0, "character": 0 },
      "end": { "line": 10, "character": 0 }
    }
  }
}

7. codeql_references

Find all references to a symbol at a specific position.

{
  "tool": "codeql_references",
  "arguments": {
    "file_uri": "file:///workspace/query.ql",
    "line": 3,
    "character": 10
  }
}

8. codeql_update_file

Update the content of an open file.

{
  "tool": "codeql_update_file",
  "arguments": {
    "file_uri": "file:///workspace/query.ql",
    "content": "import javascript\n\nfrom Function f\nwhere f.getName() = \"eval\"\nselect f, \"Dangerous eval usage\""
  }
}

9. codeql_set_workspace

Set workspace folders for better CodeQL analysis.

{
  "tool": "codeql_set_workspace",
  "arguments": {
    "folders": ["/path/to/codeql/libraries", "/path/to/project"]
  }
}

Citation

This MCP server was developed as part of the framework for our paper QLCoder. Consider citing our paper. `` @misc{wang2025qlcoderquerysynthesizerstatic, title={QLCoder: A Query Synthesizer For Static Analysis of Security Vulnerabilities}, author={Claire Wang and Ziyang Li and Saikat Dutta and Mayur Naik}, year={2025}, eprint={2511.08462}, archivePrefix={arXiv}, primaryClass={cs.CR}, url={https://arxiv.org/abs/2511.08462}, } ``