gemcp

MCP tools for RubyGems package intelligence. Ask about gems, versions, dependencies, and ownership. Get structured, provenance-tagged answers an agent can trust.

Install

gem install gemcp

MCP client config

Add to your MCP client (Claude Desktop, Kiro, etc.):

{
  "mcpServers": {
    "gemcp": {
      "command": "gemcp"
    }
  }
}

That's it. If your Ruby isn't on the default PATH, use the full path:

{
  "mcpServers": {
    "gemcp": {
      "command": "/path/to/gemcp"
    }
  }
}

Find it with gem which gemcp && which gemcp.

What it does

gemcp reads from installed gemspecs first, a persistent disk cache second, and the RubyGems.org API only when neither has what you need.

Tools

Example questions

These are the kinds of questions gemcp helps an agent answer with authoritative data:

• "Is sidekiq still actively maintained? Who owns it on RubyGems?"
• "What Ruby version does nokogiri 1.18.8 require?"
• "Can authlogic 3.6 coexist with Rails 8?"
• "What changed in authlogic's dependencies between version 3.6.1 and 6.6.0?"
• "What gems depend on rack?"
• "Show me every release of rails between 7.0.0 and 8.0.0"
• "Compare puma and unicorn — versions, owners, dependency counts"
• "What are the runtime dependencies of rails 8.1?"
• "Build me a dependency graph for sidekiq at depth 2"
• "Find me gems for background job processing"

How it resolves data

installed gemspecs
      ↓ miss
fresh disk cache
      ↓ stale/miss
conditional RubyGems.org req