Tree-Hugger-JS MCP Server

An MCP (Model Context Protocol) server that provides AI agents with powerful JavaScript/TypeScript code analysis and transformation capabilities using the tree-hugger-js library.

Features

🔍 Code Analysis

• Parse JavaScript, TypeScript, JSX, and TSX files or code strings
• Find patterns using intuitive syntax (e.g., function, class[name="MyClass"])
• Extract functions, classes, imports with detailed metadata
• Navigate AST nodes and analyze code structure
• Get nodes at specific positions

🔧 Code Transformation

• Rename identifiers throughout code
• Remove unused imports
• Chain multiple transformations
• Insert code before/after patterns
• Preview transformations before applying

📊 Code Intelligence

• Scope analysis and variable binding
• Pattern matching with CSS-like selectors
• Support for async functions, classes, methods
• TypeScript type import handling

Installation & Usage

🚀 Quick Start (Recommended)

Try immediately with npx - no installation required:

# Use with Claude Code or any MCP client
npx tree-hugger-js-mcp

📦 Global Installation

# Install globally for repeated use
npm install -g tree-hugger-js-mcp

# Then run anywhere
tree-hugger-js-mcp

🔧 Development Setup

# Clone and build from source
git clone https://github.com/qckfx/tree-hugger-js-mcp.git
cd tree-hugger-js-mcp
npm install
npm run build
npm start

MCP Client Configuration

Using with Claude Code

Add to your MCP client configuration:

{
  "mcpServers": {
    "tree-hugger-js": {
      "command": "npx",
      "args": ["tree-hugger-js-mcp"]
    }
  }
}

Alternative Configurations

{
  "mcpServers": {
    "tree-hugger-js": {
      // If installed globally
      "command": "tree-hugger-js-mcp"
      
      // Or if built from source
      "command": "node",
      "args": ["/path/to/tree-hugger-js-mcp/build/index.js"]
    }
  }
}

Tools

Code Analysis Tools

parse_code

Parse JavaScript/TypeScript code from file or string.

Parameters:

• source (string): File path or code string to parse
• isFilePath (boolean, optional): Whether source is a file path (auto-detected if not provided)
• language (string, optional): Language to use (javascript, typescript, jsx, tsx)

Example:

// Parse a file
await callTool("parse_code", { 
  source: "./src/app.js",
  isFilePath: true 
});

// Parse code string
await callTool("parse_code", { 
  source: "function hello() { console.log('world'); }" 
});

find_pattern

Find first node matching a pattern.

Parameters:

• pattern (string): Pattern to match using tree-hugger-js syntax

Examples:

// Find any function
await callTool("find_pattern", { pattern: "function" });

// Find async functions
await callTool("find_pattern", { pattern: "function[async]" });

// Find class by name
await callTool("find_pattern", { pattern: "class[name='MyClass']" });

find_all_pattern

Find all nodes matching a pattern.

Parameters:

• pattern (string): Pattern to match
• limit (number, optional): Maximum matches to return

get_functions

Get all functions with details.

Parameters:

• includeAnonymous (boolean, optional): Include anonymous functions (default: true)
• asyncOnly (boolean, optional): Only return async functions (default: false)

get_classes

Get all classes with methods and properties.

Parameters:

• includeProperties (boolean, optional): Include class properties (default: true)
• includeMethods (boolean, optional): Include class methods (default: true)

get_imports

Get all import statements.

Parameters:

• includeTypeImports (boolean, optional): Include TypeScript type-only imports (default: true)

Code Transformation Tools

rename_identifier

Rename all occurrences of an identifier.

Parameters:

• oldName (string): Current identifier name
• newName (string): New identifier name
• preview (boolean, optional): Return preview only (default: false)

Example:

await callTool("rename_identifier", {
  oldName: "fetchData",
  newName: "fetchUserData",
  preview: true
});

remove_unused_imports

Remove unused import statements.

Parameters:

• preview (boolean, optional): Return preview only (default: false)

transform_code

Apply multiple transformations in sequence.

Parameters:

• operations (array): Array of transformation operations
• preview (boolean, optional): Return preview only (default: false)

Example:

await callTool("transform_code", {
  operations: [
    { type: "rename", parameters: { oldName: "oldFunc", newName: "newFunc" } },
    { type: "removeUnusedImports" },
    { type: "replaceIn", parameters: { nodeType: "string", pattern: /localhost/g, replacement: "api.example.com" } }
  ],
  preview: true
});

insert_code

Insert code before or after nodes matching a pattern.

Parameters:

• pattern (string): Pattern to match for insertion points
• code (string): Code to insert
• position (string): "before" or "after"
• preview (boolean, optional): Return preview only (default: false)

Navigation Tools

get_node_at_position

Get AST node at specific line and column.

Parameters:

• line (number): Line number (1-based)
• column (number): Column number (0-based)

analyze_scopes

Analyze variable scopes and bindings.

Parameters:

• includeBuiltins (boolean, optional): Include built-in identifiers (default: false)

Resources

The server provides three resources for accessing internal state:

ast://current

Current parsed AST state with metadata and statistics.

ast://analysis

Results from the most recent code analysis (functions, classes, imports).

ast://transforms

History of code transformations and available operations.

Pattern Syntax

Tree-hugger-js uses intuitive patterns instead of verbose tree-sitter node types:

Basic Patterns

• function - Any function (declaration, expression, arrow, method)
• class - Class declarations and expressions
• string - String and template literals
• import/export - Import/export statements
• call - Function calls
• loop - For, while, do-while loops

Attribute Selectors

• [name="foo"] - Nodes with specific name
• [async] - Async functions
• [text*="test"] - Nodes containing text

CSS-like Selectors

• class method - Methods inside classes
• function > return - Return statements directly in functions
• :has() and :not() pseudo-selectors

Examples

Basic Code Analysis

// Parse and analyze a React component
await callTool("parse_code", { source: "./components/UserProfile.jsx" });

// Get all functions
const functions = await callTool("get_functions", { asyncOnly: true });

// Find JSX elements
const jsxElements = await callTool("find_all_pattern", { pattern: "jsx" });

Code Refactoring

// Rename a function and remove unused imports
await callTool("transform_code", {
  operations: [
    { type: "rename", parameters: { oldName: "getUserData", newName: "fetchUserProfile" } },
    { type: "removeUnusedImports" }
  ]
});

Pattern Matching

// Find all async functions that call console.log
await callTool("find_all_pattern", { 
  pattern: "function[async]:has(call[text*='console.log'])" 
});

// Find classes with constructor methods
await callTool("find_all_pattern", { 
  pattern: "class:has(method[name='constructor'])" 
});

Development

# Install dependencies
npm install

# Build the project
npm run build

# Watch mode for development
npm run dev

# Test with MCP inspector
npm run inspector

Error Handling

The server provides detailed error messages and suggestions:

• File not found errors for invalid file paths
• Parse errors with helpful context
• Pattern matching errors with suggestions
• Transformation errors with rollback capability

License

MIT