BundlerMCP

1# BundlerMCP
2 
3A Model Context Protocol (MCP) server enabling AI agents to query information about dependencies in a Ruby project's `Gemfile`. Built with [fast-mcp](https://github.com/yjacquin/fast-mcp).
4 
5[![CI](https://github.com/subelsky/bundler_mcp/actions/workflows/main.yml/badge.svg)](https://github.com/subelsky/bundler_mcp/actions/workflows/main.yml)
6[![Gem Version](https://badge.fury.io/rb/bundler_mcp.svg)](https://badge.fury.io/rb/bundler_mcp)
7 
8## Installation
9 
10Install the gem and add to the application's Gemfile by executing:
11 
12```bash
13bundle add bundler_mcp --group=development
14```
15 
16## Usage
17 
181. Generate the binstub:
19 
20```bash
21bundle binstubs bundler_mcp
22```
23 
242. Configure your client to execute the binstub. Here are examples that work for Claude and Cursor:
25 
26### Basic Example (mcp.json)
27 
28```json
29{
30  "mcpServers": {
31    "bundler-mcp": {
32      "command": "/Users/mike/my_project/bin/bundler_mcp"
33    }
34  }
35}
36```
37 
38### Example with logging and explicit Gemfile
39 
40```json
41{
42  "mcpServers": {
43    "bundler-mcp": {
44      "command": "/Users/mike/my_project/bin/bundler_mcp",
45 
46      "env": {
47        "BUNDLER_MCP_LOG_FILE": "/Users/mike/my_project/log/mcp.log",
48        "BUNDLE_GEMFILE": "/Users/mike/my_project/subdir/Gemfile"
49      }
50    }
51  }
52}
53```
54 
55### Documentation
56 
57[Available on RubyDoc](https://www.rubydoc.info/gems/bundler_mcp/)
58 
59### Available Tools
60 
61The server provides two tools for AI agents:
62 
63#### list_project_gems
64 
65Lists all bundled Ruby gems with their:
66 
67- Versions
68- Descriptions
69- Installation paths
70- Top-level documentation locations (e.g. `README` and `CHANGELOG`)
71 
72![list_project_gems tool](/docs/list_project_gems.png)
73 
74#### get_gem_details
75 
76Retrieves detailed information about a specific gem, including:
77 
78- Version
79- Description
80- Installation path
81- Top-level documentation locations
82- Source code file locations
83 
84![get_gem_details tool](/docs/get_gem_details.png)
85 
86## Environment Variables
87 
88- `BUNDLE_GEMFILE`: Used by Bundler to locate your Gemfile. If you use the binstub method described in the [Usage](#usage) section, this is usually not needed.
89- `BUNDLER_MCP_LOG_FILE`: Path to log file. Useful for troubleshooting (defaults to no logging)
90 
91## Development
92 
93After 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.
94 
95### Testing with the MCP Inspector
96 
97You can test the server directly using the [MCP inspector](https://modelcontextprotocol.io/docs/tools/inspector):
98 
99```bash
100# Basic usage
101npx @modelcontextprotocol/inspector ./bin/bundler_mcp
102 
103# With logging enabled
104BUNDLER_MCP_LOG_FILE=/tmp/log/mcp.log npx @modelcontextprotocol/inspector ./bin/bundler_mcp
105 
106# With custom Gemfile
107BUNDLE_GEMFILE=./other/Gemfile npx @modelcontextprotocol/inspector ./bin/bundler_mcp
108```
109 
110### Release Process
111 
112To install this gem onto your local machine, run `bundle exec rake install`. To release a new version:
113 
1141. Update the version number in `version.rb`
1152. Run `bundle exec rake release`
116 
117This will:
118 
119- Create a git tag for the version
120- Push git commits and the created tag
121- Push the `.gem` file to [rubygems.org](https://rubygems.org)
122 
123## Contributing
124 
125Bug reports and pull requests are welcome on GitHub at https://github.com/subelsky/bundler_mcp.
126 
127## License
128 
129Open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).
130 
131## Author
132 
133[Mike Subelsky](https://subelsky.com)
134