rubygems_mcp

Ruby gem providing RubyGems and Ruby version information via MCP (Model Context Protocol) server tools. Integrates with MCP-compatible clients like Cursor IDE, Claude Desktop, and other MCP-enabled tools.

This gem accesses public RubyGems and Ruby version information, no authentication required.

Sponsored by Kisko Labs.

• Ruby 3.1 or higher (Ruby 3.0 and earlier are not supported)

gem install rubygems_mcp

For Cursor IDE, create or update .cursor/mcp.json in your project:

{
  "mcpServers": {
    "rubygems": {
      "command": "rubygems_mcp"
    }
  }
}

For Claude Desktop, edit the MCP configuration file:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "rubygems": {
      "command": "rubygems_mcp"
    }
  }
}

Note: After updating the configuration, restart Claude Desktop for changes to take effect.

You can test the MCP server using the MCP Inspector tool:

# Run the MCP inspector with the server
npx @modelcontextprotocol/inspector bundle exec rubygems_mcp

The inspector will:

1. Start a proxy server and open a browser interface
2. Connect to your MCP server via STDIO
3. Allow you to test all available tools interactively
4. Display request/response messages and any errors

This is useful for:

• Testing tool functionality before integrating with MCP clients
• Debugging MCP protocol communication
• Exploring available tools and their parameters

After installation, you can start the MCP server immediately:

# With bundler
gem install rubygems_mcp && bundle exec rubygems_mcp

# Or if installed globally
rubygems_mcp

The server will start and communicate via STDIN/STDOUT using the MCP protocol.

• RubyGems API Client: Full-featured client for RubyGems REST API with comprehensive endpoint coverage
• Ruby Version Information: Fetch Ruby release information, changelogs, and maintenance status from ruby-lang.org
• MCP Server Integration: Ready-to-use MCP server with 19 tools and 4 resources, compatible with Cursor IDE, Claude Desktop, and other MCP-enabled tools
• Pagination & Sorting: Support for large result sets with customizable pagination and sorting options
• Caching: In-memory caching with configurable TTL for improved performance
• Error Handling: Graceful error handling with custom exceptions and response size limits
• No Authentication Required: All endpoints are public, no API keys needed
• Comprehensive API Coverage: Supports gem versions, latest versions, Ruby versions, gem search, gem information, reverse dependencies, download statistics, changelogs, and more

require "rubygems_mcp"

# Create client
client = RubygemsMcp::Client.new

# Get latest versions for multiple gems
versions = client.get_latest_versions(["rails", "nokogiri", "rack"])
# => [
#   { name: "rails", version: "7.1.0", release_date: #<Date>, license: "MIT" },
#   { name: "nokogiri", version: "1.15.0", release_date: #<Date>, license: "MIT" },
#   { name: "rack", version: "3.0.0", release_date: #<Date>, license: "MIT" }
# ]

# Get all versions for a gem
versions = client.get_gem_versions("rails")
# => [
#   { version: "7.1.0", release_date: #<Date>, license: "MIT" },
#   { version: "7.0.8", release_date: #<Date>, license: "MIT" },
#   ...
# ]

# Get latest Ruby version
ruby_version = client.get_latest_ruby_version
# => { version: "3.3.0", release_date: #<Date> }

# Get all Ruby versions
ruby_versions = client.get_ruby_versions
# => [
#   { version: "3.3.0", release_date: #<Date> },
#   { version: "3.2.0", release_date: #<Date> },
#   ...
# ]

# Get gem information
gem_info = client.get_gem_info("rails")
# => {
#   name: "rails",
#   version: "7.1.0",
#   summary: "Full-stack web application framework.",
#   homepage: "https://rubyonrails.org",
#   source_code: "https://github.com/rails/rails",
#   documentation: "https://api.rubyonrails.org",
#   licenses: ["MIT"],
#   authors: ["David Heinemeier Hansson", ...]
# }

# Search for gems
results = client.search_gems("rails")
# => [
#   { name: "rails", version: "7.1.0", info: "...", ... },
#   { name: "rails_admin", version: "3.0.0", info: "...", ... },
#   ...
# ]

# Get reverse dependencies
reverse_deps = client.get_gem_reverse_dependencies("rails")
# => ["rails_admin", "activeadmin", ...]

# Get download statistics
downloads = client.get_gem_version_downloads("rails", "7.1.0")
# => { version_downloads: 123456, total_downloads: 987654321 }

# Get Ruby maintenance status
maintenance = client.get_ruby_maintenance_status
# => [
#   { version: "3.4", status: "normal maintenance", release_date: "2024-12-25", ... },
#   { version: "3.3", status: "normal maintenance", ... },
#   ...
# ]

# Get Ruby version changelog
changelog = client.get_ruby_version_changelog("3.4.7")
# => { version: "3.4.7", summary: "...", release_notes_url: "..." }

# Get latest/recently updated gems
latest = client.get_latest_gems(limit: 10)
recently_updated = client.get_recently_updated_gems(limit: 10)

• get_latest_versions(gem_names, fields: nil) - Get latest versions for a list of gems with release dates and licenses. Supports GraphQL-like field selection.
• get_gem_versions(gem_name, limit: nil, offset: 0, sort: :version_desc, fields: nil) - Get all versions for a single gem with release dates and licenses, sorted by version descending. Supports pagination, sorting, and field selection.

• get_latest_ruby_version - Get latest Ruby version with release date
• get_ruby_versions(limit: nil, offset: 0, sort: :version_desc) - Get all Ruby versions with release dates, download URLs, and release notes URLs, sorted by version descending. Supports pagination and sorting.
• get_ruby_version_changelog(version) - Get changelog summary for a specific Ruby version by fetching and parsing the release notes
• get_ruby_version_github_changelog(version) - Get GitHub release changelog for a Ruby version from the ruby/ruby repository
• get_ruby_roadmap - Get Ruby roadmap information from bugs.ruby-lang.org showing planned versions and their issues
• get_ruby_version_roadmap_details(version) - Get detailed roadmap information for a specific Ruby version from bugs.ruby-lang.org, including issues and features planned for that version
• get_ruby_maintenance_status - Get maintenance status for all Ruby versions including EOL dates and maintenance phases

• get_gem_info(gem_name, fields: nil) - Get detailed information about a gem (summary, homepage, source code, documentation, licenses, authors, dependencies, downloads). Supports GraphQL-like field selection.
• get_gem_version_info(gem_name, version, fields: nil) - Get detailed information for a specific gem version using RubyGems API v2 (version-specific downloads, dependencies, SHA checksums, creation date, built date). Supports GraphQL-like field selection.
• get_gem_reverse_dependencies(gem_name) - Get reverse dependencies - list of gems that depend on the specified gem
• get_gem_version_downloads(gem_name, version) - Get download statistics for a specific gem version
• get_gem_changelog(gem_name, version: nil) - Get changelog summary for a gem by fetching and parsing the changelog from its changelog_uri
• search_gems(query, limit: nil, offset: 0) - Search for gems by name on RubyGems. Supports pagination.

• get_latest_gems(limit: 30) - Get latest gems - most recently added gems to RubyGems.org
• get_recently_updated_gems(limit: 30) - Get recently updated gems - most recently updated gem versions

This gem includes a ready-to-use MCP server that can be run directly:

# After installing the gem
bundle exec rubygems_mcp

Or if installed globally:

gem install rubygems_mcp
rubygems_mcp

The server will communicate via STDIN/STDOUT using the MCP protocol. Configure it in your MCP client (e.g., Cursor IDE, Claude Desktop, or other MCP-enabled tools).

The MCP server provides the following tools:

1. get_latest_versions - Get latest versions for a list of gems with release dates and licenses. Supports GraphQL-like field selection.

   • Parameters: gem_names (array of strings), fields (optional array of strings)

2. get_gem_versions - Get all versions for a single gem with release dates and licenses, sorted by version descending. Supports GraphQL-like field selection.

   • Parameters: gem_name (string), limit (optional integer), offset (optional integer), sort (optional string: "version_desc", "version_asc", "date_desc", "date_asc"), fields (optional array of strings)

3. get_latest_ruby_version - Get latest Ruby version with release date

   • Parameters: none

4. get_ruby_versions - Get all Ruby versions with release dates, download URLs, and release notes URLs, sorted by version descending

   • Parameters: limit (optional integer), offset (optional integer), sort (optional string: "version_desc", "version_asc", "date_desc", "date_asc")

5. get_ruby_version_changelog - Get changelog summary for a specific Ruby version by fetching and parsing the release notes

   • Parameters: version (string, e.g., "3.4.7")

6. get_gem_info - Get detailed information about a gem (summary, homepage, source code, documentation, licenses, authors, dependencies, downloads). Supports GraphQL-like field selection.

   • Parameters: gem_name (string), fields (optional array of strings)

7. get_gem_version_info - Get detailed information for a specific gem version using RubyGems API v2 (version-specific downloads, dependencies, SHA checksums, creation date, built date). Supports GraphQL-like field selection.

   • Parameters: gem_name (string), version (string, e.g., "0.1.0" or "1.15.0-x86_64-linux"), fields (optional array of strings)

8. get_gem_reverse_dependencies - Get reverse dependencies - list of gems that depend on the specified gem

   • Parameters: gem_name (string)

9. get_gem_version_downloads - Get download statistics for a specific gem version

   • Parameters: gem_name (string), version (string)

10. get_latest_gems - Get latest gems - most recently added gems to RubyGems.org

• Parameters: limit (optional integer, default: 30, max: 50)

11. get_recently_updated_gems - Get recently updated gems - most recently updated gem versions

• Parameters: limit (optional integer, default: 30, max: 50)

12. get_gem_changelog - Get changelog summary for a gem by fetching and parsing the changelog from its changelog_uri

• Parameters: gem_name (string), version (optional string, uses latest if not provided)

13. search_gems - Search for gems by name on RubyGems

• Parameters: query (string)

14. get_ruby_roadmap - Get Ruby roadmap information from bugs.ruby-lang.org showing planned versions and their issues

• Parameters: none

15. get_ruby_version_roadmap_details - Get detailed roadmap information for a specific Ruby version from bugs.ruby-lang.org, including issues and features planned for that version

• Parameters: version (string, e.g., "3.4", "4.0")

16. get_ruby_version_github_changelog - Get GitHub release changelog for a Ruby version from the ruby/ruby repository

• Parameters: version (string, e.g., "3.4.7", "3.4.0")

The MCP server provides the following resources:

1. rubygems://popular - A curated list of popular Ruby gems with their latest versions

   • Resource name: "Popular Ruby Gems"
   • MIME type: application/json

2. rubygems://ruby/compatibility - Information about Ruby version compatibility and release dates

   • Resource name: "Ruby Version Compatibility"
   • MIME type: application/json

3. rubygems://ruby/maintenance - Detailed maintenance status for all Ruby versions including EOL dates and maintenance phases

   • Resource name: "Ruby Maintenance Status"
   • MIME type: application/json

4. rubygems://ruby/latest - The latest stable Ruby version with release date

   • Resource name: "Latest Ruby Version"
   • MIME type: application/json

The client handles errors gracefully:

• Returns empty arrays for failed requests
• Returns empty hashes for failed gem info requests
• Handles network errors and JSON parsing errors

# Install dependencies
bundle install

# Run tests
bundle exec rspec

# Run tests across multiple Ruby versions
bundle exec appraisal install
bundle exec appraisal rspec

# Run linting
bundle exec standardrb --fix

# Validate RBS type signatures
bundle exec rbs validate

Bug reports and pull requests are welcome on GitHub at https://github.com/amkisko/rubygems_mcp.rb.

Contribution policy:

• New features are not necessarily added to the gem
• Pull request should have test coverage for affected parts
• Pull request should have changelog entry

Review policy:

• It might take up to 2 calendar weeks to review and merge critical fixes
• It might take up to 6 calendar months to review and merge pull request
• It might take up to 1 calendar year to review an issue

For more information, see CONTRIBUTING.md.

If you discover a security vulnerability, please report it responsibly. See SECURITY.md for details.

The gem is available as open source under the terms of the MIT License.