subelsky/bundler_mcp

A Model Context Protocol (MCP) server enabling AI agents to query information about dependencies in a Ruby project's Gemfile. Built with fast-mcp.
Installation
Install the gem and add to the application's Gemfile by executing:
Usage
1. Generate the binstub:
2. Configure your client to execute the binstub. Here are examples that work for Claude and Cursor:
Basic Example (mcp.json)
Example with logging and explicit Gemfile
Documentation
Available on RubyDoc
Available Tools
The server provides two tools for AI agents:
list_project_gems
Lists all bundled Ruby gems with their:
- Versions
- Descriptions
- Installation paths
- Top-level documentation locations (e.g. README and CHANGELOG)
get_gem_details
Retrieves detailed information about a specific gem, including:
- Version
- Description
- Installation path
- Top-level documentation locations
- Source code file locations
Environment Variables
- BUNDLE_GEMFILE: Used by Bundler to locate your Gemfile. If you use the binstub method described in the Usage section, this is usually not needed.
- BUNDLER_MCP_LOG_FILE: Path to log file. Useful for troubleshooting (defaults to no logging)
Development
After checking out the repo, run bin/setup to install dependencies and bundle exec rspec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.
Testing with the MCP Inspector
You can test the server directly using the MCP inspector:
Release Process
To install this gem onto your local machine, run bundle exec rake install. To release a new version:
1. Update the version number in version.rb
2. Run bundle exec rake release
This will:
- Create a git tag for the version
- Push git commits and the created tag
- Push the .gem file to rubygems.org
Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/subelsky/bundler_mcp.