VSCode Language Server MCP Extension

Exposes VSCode Language Server Protocol features via MCP (Model Context Protocol) for use with Claude Code.

Overview

This VSCode extension runs an MCP server that provides access to VSCode's Language Server APIs, enabling Claude Code to:

• Get document symbol outlines
• Find all references to symbols
• Rename symbols with full reference tracking
• Get symbol definitions
• Get hover information (types, docs)

Features

MCP Tools Provided:

• vscode_ls_get_symbols - Get complete symbol outline of a file
• vscode_ls_find_references - Find all references to a symbol
• vscode_ls_rename - Safely rename symbols with reference tracking
• vscode_ls_get_definition - Get definition location for a symbol
• vscode_ls_get_hover - Get type information and documentation

Benefits:

• Language-aware symbol renaming (not just find/replace)
• Cross-file reference tracking
• Type information from TypeScript/JavaScript language server
• Scope-aware analysis
• Battle-tested VSCode rename functionality

Installation

Step 1: Install Dependencies

cd ~/source/vscode-mcp-language-server
npm install

Step 2: Compile TypeScript

npm run compile

Step 3: Install Extension in VSCode

Option A: Development Mode

1. Open this directory in VSCode
2. Press F5 to launch Extension Development Host
3. The extension will be active in the new window

Option B: Install Locally

npm run package
code --install-extension vscode-mcp-language-server-0.1.0.vsix

Configuration

The extension can be configured in VSCode settings:

{
  "vscodeMcpLs.enabled": true,
  "vscodeMcpLs.port": 3100,
  "vscodeMcpLs.logLevel": "info"
}

Settings:

• enabled - Enable/disable the MCP server
• port - Port number for MCP server (default: 3100)
• logLevel - Logging level: debug, info, warn, error

Usage

Check Extension Status

Use the status bar item (bottom-right) or command palette:

• VSCode MCP LS: Show Status - Display current status
• VSCode MCP LS: Restart Server - Restart the MCP server

Connecting from Claude Code

Add to your project's MCP configuration in ~/.claude.json:

{
  "projects": {
    "/your/project/path": {
      "mcpServers": {
        "vscode-language-server": {
          "type": "http",
          "url": "http://localhost:3100"
        }
      }
    }
  }
}

Or use the CLI (note: manual configuration is currently required as claude mcp add doesn't support custom HTTP servers yet):

# Test the connection first
curl http://localhost:3100
# Should return: {"name":"vscode-mcp-language-server","version":"0.1.0","status":"running","transport":"http"}

Using with Unminification Plugin

The unminification plugin skills will automatically use these tools when available:

# In analyze-minified-symbols skill:

### Step 2: Query VSCode for symbol outline

Use MCP tool:
\`\`\`
mcp__vscode_language_server__vscode_ls_get_symbols({
  "uri": "file:///path/to/minified.js"
})
\`\`\`

Returns:
\`\`\`json
{
  "symbols": [
    {
      "name": "Fbr",
      "kind": "Variable",
      "range": { "start": { "line": 49, "character": 6 }, ... },
      "children": []
    }
  ]
}
\`\`\`

MCP Tools Reference

vscode_ls_get_symbols

Get document symbol outline.

Parameters:

{
  "uri": "file:///absolute/path/to/file.js"
}

Returns:

{
  "symbols": [
    {
      "name": "functionName",
      "kind": "Function",
      "range": { "start": { "line": 10, "character": 0 }, "end": {...} },
      "selectionRange": {...},
      "children": [...]
    }
  ]
}

vscode_ls_find_references

Find all references to a symbol.

Parameters:

{
  "uri": "file:///path/to/file.js",
  "line": 49,
  "character": 6
}

Returns:

{
  "references": [
    {
      "uri": "file:///path/to/file.js",
      "range": { "start": { "line": 49, "character": 6 }, "end": {...} }
    }
  ]
}

vscode_ls_rename

Rename symbol with full reference tracking.

Parameters:

{
  "uri": "file:///path/to/file.js",
  "line": 49,
  "character": 6,
  "newName": "isWindowsPlatform"
}

Returns:

{
  "success": true,
  "changesCount": 15,
  "changes": [
    {
      "uri": "file:///path/to/file.js",
      "range": {...},
      "newText": "isWindowsPlatform"
    }
  ]
}

vscode_ls_get_definition

Get definition location for a symbol.

Parameters:

{
  "uri": "file:///path/to/file.js",
  "line": 100,
  "character": 10
}

Returns:

{
  "definitions": [
    {
      "uri": "file:///path/to/file.js",
      "range": { "start": { "line": 49, "character": 6 }, "end": {...} }
    }
  ]
}

vscode_ls_get_hover

Get type information and documentation.

Parameters:

{
  "uri": "file:///path/to/file.js",
  "line": 100,
  "character": 10
}

Returns:

{
  "hover": {
    "contents": [
      {
        "kind": "markdown",
        "value": "```typescript\nconst isWindowsPlatform: boolean\n```"
      }
    ],
    "range": {...}
  }
}

Development

Build

npm run compile

Watch Mode

npm run watch

Debug

1. Open in VSCode
2. Press F5 to launch Extension Development Host
3. Set breakpoints in source files
4. Extension runs with debugger attached

Testing

Test the MCP server manually:

# Start VSCode with extension
# In another terminal, test connection:
wscat -c ws://localhost:3100

# Send test request:
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/list"
}

Architecture

VSCode Extension
 extension.ts          # Entry point, activation
 mcpServer.ts          # MCP HTTP server
 languageServerTools.ts # VSCode API wrappers
 logger.ts             # Logging utility

VSCode Language Server APIs
 accessed via vscode.commands.executeCommand
 vscode.executeDocumentSymbolProvider
 vscode.executeReferenceProvider
 vscode.executeDocumentRenameProvider
 vscode.executeDefinitionProvider
 vscode.executeHoverProvider

MCP Protocol
 exposed via HTTP on port 3100
Claude Code
 Uses tools via MCP client

Troubleshooting

Extension Not Starting

Check VSCode Output panel:

1. View Output
2. Select "VSCode MCP Language Server" from dropdown
3. Check for error messages

MCP Server Not Responding

1. Check extension is enabled: vscodeMcpLs.enabled
2. Check port is not in use: lsof -i :3100
3. Restart server: Command Palette "VSCode MCP LS: Restart Server"

Symbol Operations Not Working

1. Ensure language server is active (TypeScript/JavaScript files)
2. Check file is saved and indexed
3. Verify file URI format: file:///absolute/path

Future Enhancements

• Support for more language servers (Python, Go, etc.)
• Workspace-wide symbol search
• Code actions and quick fixes
• Signature help
• Completion provider access
• Authentication for MCP connections

Contributing

Issues and pull requests welcome!

License

MIT