Summary
Connects Claude to Martin Fowler's catalog of 71+ refactorings through a language-agnostic architecture. You get five tools: list available refactorings by category, preview changes before applying them, execute refactorings on your codebase, inspect code structure at class or method level, and analyze for code smells. Targets are specified with native conventions like `src/order.py::Order::calculate_total#L10-L15`. Currently supports Python through the molting-cli backend with Ruby, Java, and Go planned. Useful when you want programmatic refactoring suggestions and execution instead of manual restructuring, or when working through technical debt systematically. Output uses TOON format for token efficiency.
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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
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-clifor 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.
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