mcpbeat Sign in

Andrew Kane Gem Writer Skill for Claude

Write Ruby gems following Andrew Kane's proven patterns and philosophy. Use when creating new Ruby gems, refactoring existing gems, designing gem APIs, or when the user wants clean, minimal, production-ready Ruby library code. Triggers on requests like "create a gem", "write a Ruby library", "design a gem API", or mentions of Andrew Kane's style.

1k tokens
context cost
the whole folder, loaded on every use
2
files
instructions only
0
copies elsewhere
how many repositories repackaged it
320
stars on the repo
on the repository, not the skill itself

Install

one command, takes just this skill from the repository
npx skills add https://github.com/Microck/ordinary-claude-skills --skill andrew-kane-gem-writer

What comes with it

910 bytes besides the instruction
metadata.json

The instruction itself

11 sections, as written by the author

Andrew Kane Gem Writer

Write Ruby gems following Andrew Kane's battle-tested patterns from 100+ gems with 374M+ downloads (Searchkick, PgHero, Chartkick, Strong Migrations, Lockbox, Ahoy, Blazer, Groupdate, Neighbor, Blind Index).

Core Philosophy

Simplicity over cleverness. Zero or minimal dependencies. Explicit code over metaprogramming. Rails integration without Rails coupling. Every pattern serves production use cases.

Entry Point Structure

Every gem follows this exact pattern in lib/gemname.rb:

# 1. Dependencies (stdlib preferred)
require "forwardable"

# 2. Internal modules
require_relative "gemname/model"
require_relative "gemname/version"

# 3. Conditional Rails (CRITICAL - never require Rails directly)
require_relative "gemname/railtie" if defined?(Rails)

# 4. Module with config and errors
module GemName
  class Error < StandardError; end
  class InvalidConfigError < Error; end

  class << self
    attr_accessor :timeout, :logger
    attr_writer :client
  end

  self.timeout = 10  # Defaults set immediately
end

Class Macro DSL Pattern

The signature Kane pattern—single method call configures everything:

# Usage
class Product < ApplicationRecord
  searchkick word_start: [:name]
end

# Implementation
module GemName
  module Model
    def gemname(**options)
      unknown = options.keys - KNOWN_KEYWORDS
      raise ArgumentError, "unknown keywords: #{unknown.join(", ")}" if unknown.any?

      mod = Module.new
      mod.module_eval do
        define_method :some_method do
          # implementation
        end unless method_defined?(:some_method)
      end
      include mod

      class_eval do
        cattr_reader :gemname_options, instance_reader: false
        class_variable_set :@@gemname_options, options.dup
      end
    end
  end
end

Rails Integration

Always use ActiveSupport.on_load—never require Rails gems directly:

# WRONG
require "active_record"
ActiveRecord::Base.include(MyGem::Model)

# CORRECT
ActiveSupport.on_load(:active_record) do
  extend GemName::Model
end

# Use prepend for behavior modification
ActiveSupport.on_load(:active_record) do
  ActiveRecord::Migration.prepend(GemName::Migration)
end

Configuration Pattern

Use class << self with attr_accessor, not Configuration objects:

module GemName
  class << self
    attr_accessor :timeout, :logger
    attr_writer :master_key
  end

  def self.master_key
    @master_key ||= ENV["GEMNAME_MASTER_KEY"]
  end

  self.timeout = 10
  self.logger = nil
end

Error Handling

Simple hierarchy with informative messages:

module GemName
  class Error < StandardError; end
  class ConfigError < Error; end
  class ValidationError < Error; end
end

# Validate early with ArgumentError
def initialize(key:)
  raise ArgumentError, "Key must be 32 bytes" unless key&.bytesize == 32
end

Testing (Minitest Only)

# test/test_helper.rb
require "bundler/setup"
Bundler.require(:default)
require "minitest/autorun"
require "minitest/pride"

# test/model_test.rb
class ModelTest < Minitest::Test
  def test_basic_functionality
    assert_equal expected, actual
  end
end

Gemspec Pattern

Zero runtime dependencies when possible:

Gem::Specification.new do |spec|
  spec.name = "gemname"
  spec.version = GemName::VERSION
  spec.required_ruby_version = ">= 3.1"
  spec.files = Dir["*.{md,txt}", "{lib}/**/*"]
  spec.require_path = "lib"
  # NO add_dependency lines - dev deps go in Gemfile
end

Anti-Patterns to Avoid

  • method_missing (use define_method instead)
  • Configuration objects (use class accessors)
  • @@class_variables (use class << self)
  • Requiring Rails gems directly
  • Many runtime dependencies
  • Committing Gemfile.lock in gems
  • RSpec (use Minitest)
  • Heavy DSLs (prefer explicit Ruby)

Reference Files

For deeper patterns, see:

  • references/module-organization.md - Directory layouts, method decomposition
  • references/rails-integration.md - Railtie, Engine, on_load patterns
  • references/database-adapters.md - Multi-database support patterns
  • references/testing-patterns.md - Multi-version testing, CI setup
  • references/resources.md - Links to Kane's repos and articles

Other skills for the same job

different authors, same section of the catalogue
MCP Builder
by anthropics
vendor ×13

Guide for creating high-quality MCP (Model Context Protocol) servers that enable LLMs to interact with external services through well-designed tools. Use when building MCP servers to integrate external APIs or services, whether in Python (FastMCP) or Node/TypeScript (MCP SDK).

30k tokens scripts
Changelog Generator
by frostant
×9

Automatically creates user-facing changelogs from git commits by analyzing commit history, categorizing changes, and transforming technical commits into clear, customer-friendly release notes. Turns hours of manual changelog writing into minutes of automated generation.

774 tokens
Finishing A Development Branch
by ZhanlinCui
×7

Use when implementation is complete, all tests pass, and you need to decide how to integrate the work - guides completion of development work by presenting structured options for merge, PR, or cleanup

1k tokens
MCP Builder
by JayZeeDesign
×7

Guide for creating high-quality MCP (Model Context Protocol) servers that enable LLMs to interact with external services through well-designed tools. Use when building MCP servers to integrate external APIs or services, whether in Python (FastMCP) or Node/TypeScript (MCP SDK).

37k tokens scripts
Vercel React Native Skills
by vercel-labs
vendor ×6

React Native and Expo best practices for building performant mobile apps. Use when building React Native components, optimizing list performance, implementing animations, or working with native modules. Triggers on tasks involving React Native, Expo, mobile performance, or native platform APIs.

39k tokens
Vercel React Best Practices
by ratacat
×5

React and Next.js performance optimization guidelines from Vercel Engineering. This skill should be used when writing, reviewing, or refactoring React/Next.js code to ensure optimal performance patterns. Triggers on tasks involving React components, Next.js pages, data fetching, bundle optimization, or performance improvements.

34k tokens
Next Best Practices
by vercel-labs
vendor ×4

Next.js best practices - file conventions, RSC boundaries, data patterns, async APIs, metadata, error handling, route handlers, image/font optimization, bundling

20k tokens
Using Git Worktrees
by ZhanlinCui
×4

Use when starting feature work that needs isolation from current workspace or before executing implementation plans - creates isolated git worktrees with smart directory selection and safety verification

1k tokens

How to use it

Copy the folder

Take microck/andrew-kane-gem-writer from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

The agent identifies a skill by the name field in its header. Two skills with the same name cannot sit side by side — one of them will be ignored.