mcp-refactoring

An MCP (Model Context Protocol) server that exposes Martin Fowler's refactoring catalog to LLMs through a pluggable, language-agnostic architecture.

Features

• 71+ Refactorings: Full implementation of Martin Fowler's refactoring catalog

• Pluggable Architecture: Support for multiple languages (Python first, Ruby/Java/Go planned)

• Safe by Default: Preview mode shows changes before applying

• LLM-Optimized: TOON output format for token efficiency

Related MCP server: Code Search MCP

Installation

# Using uvx (recommended)
uvx mcp-refactoring

# Using pip
pip install mcp-refactoring

# Using pipx
pipx install mcp-refactoring

Requirements

• Python 3.10+

• A language backend (e.g., molting-cli for Python)

Install the Python backend:

pip install molting-cli

Claude Desktop Configuration

Add to your Claude Desktop config:

{
  "mcpServers": {
    "refactoring": {
      "command": "uvx",
      "args": ["mcp-refactoring"]
    }
  }
}

Available Tools

list_refactorings

List available refactorings with their parameter contracts.

list_refactorings(language="python", category="composing_methods")

preview_refactoring

Preview what changes a refactoring would make (dry-run).

preview_refactoring(
    refactoring="extract-method",
    target="src/order.py::Order::calculate#L10-L15",
    params={"name": "calculate_tax"}
)

apply_refactoring

Apply a refactoring to the codebase.

apply_refactoring(
    refactoring="rename-method",
    target="src/order.py::Order::calc",
    params={"new_name": "calculate_total"}
)

inspect_structure

Get structural information about code.

inspect_structure(path="src/order.py", depth="method")

analyze_code

Analyze code for smells and suggest refactorings.

analyze_code(path="src/order.py", smells=["long-method"])

Target Specification

Each language uses its native conventions:

Python

src/order.py::Order::calculate_total        # Method
src/order.py::Order::calculate_total#L10-L15  # Line range
src/order.py::Order                         # Class

Configuration

Create ~/.mcp-refactoring/config.toml:

[backends.python]
enabled = true
command = "molting"

[backends.ruby]
enabled = false
command = "molting-rb"

Environment variable overrides:

MCP_REFACTORING_PYTHON_COMMAND=/path/to/molting
MCP_REFACTORING_PYTHON_ENABLED=true

Refactoring Categories

Based on Martin Fowler's catalog:

• Composing Methods: extract-method, inline-method, etc.

• Moving Features: move-method, extract-class, etc.

• Organizing Data: encapsulate-field, replace-type-code, etc.

• Simplifying Conditionals: decompose-conditional, guard-clauses, etc.

• Simplifying Method Calls: rename-method, add-parameter, etc.

• Dealing with Generalization: pull-up-method, extract-interface, etc.

Development

# Clone the repository
git clone https://github.com/marshally/mcp-refactoring.git
cd mcp-refactoring

# Install in development mode
pip install -e ".[dev]"

# Run tests
pytest

# Run linter
ruff check .

# Run type checker
mypy src/

License

MIT License - see LICENSE for details.