Ruby MCP Server Generator
Generate a complete, production-ready MCP server in Ruby using the official Ruby SDK.
Project Generation
When asked to create a Ruby MCP server, generate a complete project with this structure:
my-mcp-server/
├── Gemfile
├── Rakefile
├── lib/
│ ├── my_mcp_server.rb
│ ├── my_mcp_server/
│ │ ├── server.rb
│ │ ├── tools/
│ │ │ ├── greet_tool.rb
│ │ │ └── calculate_tool.rb
│ │ ├── prompts/
│ │ │ └── code_review_prompt.rb
│ │ └── resources/
│ │ └── example_resource.rb
├── bin/
│ └── mcp-server
├── test/
│ ├── test_helper.rb
│ └── tools/
│ ├── greet_tool_test.rb
│ └── calculate_tool_test.rb
└── README.md
Gemfile Template
source 'https://rubygems.org'
gem 'mcp', '~> 0.4.0'
group :development, :test do
gem 'minitest', '~> 5.0'
gem 'rake', '~> 13.0'
gem 'rubocop', '~> 1.50'
end
Rakefile Template
require 'rake/testtask'
require 'rubocop/rake_task'
Rake::TestTask.new(:test) do |t|
t.libs << 'test'
t.libs << 'lib'
t.test_files = FileList['test/**/*_test.rb']
end
RuboCop::RakeTask.new
task default: %i[test rubocop]
lib/my_mcp_server.rb Template
# frozen_string_literal: true
require 'mcp'
require_relative 'my_mcp_server/server'
require_relative 'my_mcp_server/tools/greet_tool'
require_relative 'my_mcp_server/tools/calculate_tool'
require_relative 'my_mcp_server/prompts/code_review_prompt'
require_relative 'my_mcp_server/resources/example_resource'
module MyMcpServer
VERSION = '1.0.0'
end
lib/my_mcp_server/server.rb Template
# frozen_string_literal: true
module MyMcpServer
class Server
attr_reader :mcp_server
def initialize(server_context: {})
@mcp_server = MCP::Server.new(
name: 'my_mcp_server',
version: MyMcpServer::VERSION,
tools: [
Tools::GreetTool,
Tools::CalculateTool
],
prompts: [
Prompts::CodeReviewPrompt
],
resources: [
Resources::ExampleResource.resource
],
server_context: server_context
)
setup_resource_handler
end
def handle_json(json_string)
mcp_server.handle_json(json_string)
end
def start_stdio
transport = MCP::Server::Transports::StdioTransport.new(mcp_server)
transport.open
end
private
def setup_resource_handler
mcp_server.resources_read_handler do |params|
Resources::ExampleResource.read(params[:uri])
end
end
end
end
lib/my_mcp_server/tools/greet_tool.rb Template
# frozen_string_literal: true
module MyMcpServer
module Tools
class GreetTool < MCP::Tool
tool_name 'greet'
description 'Generate a greeting message'
input_schema(
properties: {
name: {
type: 'string',
description: 'Name to greet'
}
},
required: ['name']
)
output_schema(
properties: {
message: { type: 'string' },
timestamp: { type: 'string', format: 'date-time' }
},
required: ['message', 'timestamp']
)
annotations(
read_only_hint: true,
idempotent_hint: true
)
def self.call(name:, server_context:)
timestamp = Time.now.iso8601
message = "Hello, #{name}! Welcome to MCP."
structured_data = {
message: message,
timestamp: timestamp
}
MCP::Tool::Response.new(
[{ type: 'text', text: message }],
structured_content: structured_data
)
end
end
end
end
lib/my_mcp_server/tools/calculate_tool.rb Template
# frozen_string_literal: true
module MyMcpServer
module Tools
class CalculateTool < MCP::Tool
tool_name 'calculate'
description 'Perform mathematical calculations'
input_schema(
properties: {
operation: {
type: 'string',
description: 'Operation to perform',
enum: ['add', 'subtract', 'multiply', 'divide']
},
a: {
type: 'number',
description: 'First operand'
},
b: {
type: 'number',
description: 'Second operand'
}
},
required: ['operation', 'a', 'b']
)
output_schema(
properties: {
result: { type: 'number' },
operation: { type: 'string' }
},
required: ['result', 'operation']
)
annotations(
read_only_hint: true,
idempotent_hint: true
)
def self.call(operation:, a:, b:, server_context:)
result = case operation
when 'add' then a + b
when 'subtract' then a - b
when 'multiply' then a * b
when 'divide'
return error_response('Division by zero') if b.zero?
a / b.to_f
else
return error_response("Unknown operation: #{operation}")
end
structured_data = {
result: result,
operation: operation
}
MCP::Tool::Response.new(
[{ type: 'text', text: "Result: #{result}" }],
structured_content: structured_data
)
end
def self.error_response(message)
MCP::Tool::Response.new(
[{ type: 'text', text: message }],
is_error: true
)
end
end
end
end
lib/my_mcp_server/prompts/code_review_prompt.rb Template
# frozen_string_literal: true
module MyMcpServer
module Prompts
class CodeReviewPrompt < MCP::Prompt
prompt_name 'code_review'
description 'Generate a code review prompt'
arguments [
MCP::Prompt::Argument.new(
name: 'language',
description: 'Programming language',
required: true
),
MCP::Prompt::Argument.new(
name: 'focus',
description: 'Review focus area (e.g., performance, security)',
required: false
)
]
meta(
version: '1.0',
category: 'development'
)
def self.template(args, server_context:)
language = args['language'] || 'Ruby'
focus = args['focus'] || 'general quality'
MCP::Prompt::Result.new(
description: "Code review for #{language} with focus on #{focus}",
messages: [
MCP::Prompt::Message.new(
role: 'user',
content: MCP::Content::Text.new(
"Please review this #{language} code with focus on #{focus}."
)
),
MCP::Prompt::Message.new(
role: 'assistant',
content: MCP::Content::Text.new(
"I'll review the code focusing on #{focus}. Please share the code."
)
),
MCP::Prompt::Message.new(
role: 'user',
content: MCP::Content::Text.new(
'[paste code here]'
)
)
]
)
end
end
end
end
lib/my_mcp_server/resources/example_resource.rb Template
# frozen_string_literal: true
module MyMcpServer
module Resources
class ExampleResource
RESOURCE_URI = 'resource://data/example'
def self.resource
MCP::Resource.new(
uri: RESOURCE_URI,
name: 'example-data',
description: 'Example resource data',
mime_type: 'application/json'
)
end
def self.read(uri)
return [] unless uri == RESOURCE_URI
data = {
message: 'Example resource data',
timestamp: Time.now.iso8601,
version: MyMcpServer::VERSION
}
[{
uri: uri,
mimeType: 'application/json',
text: data.to_json
}]
end
end
end
end
bin/mcp-server Template
#!/usr/bin/env ruby
# frozen_string_literal: true
require_relative '../lib/my_mcp_server'
begin
server = MyMcpServer::Server.new
server.start_stdio
rescue Interrupt
warn "\nShutting down server..."
exit 0
rescue StandardError => e
warn "Error: #{e.message}"
warn e.backtrace.join("\n")
exit 1
end
Make the file executable:
chmod +x bin/mcp-server
test/test_helper.rb Template
# frozen_string_literal: true
$LOAD_PATH.unshift File.expand_path('../lib', __dir__)
require 'my_mcp_server'
require 'minitest/autorun'
test/tools/greet_tool_test.rb Template
# frozen_string_literal: true
require 'test_helper'
module MyMcpServer
module Tools
class GreetToolTest < Minitest::Test
def test_greet_with_name
response = GreetTool.call(
name: 'Ruby',
server_context: {}
)
refute response.is_error
assert_equal 1, response.content.length
assert_match(/Ruby/, response.content.first[:text])
assert response.structured_content
assert_equal 'Hello, Ruby! Welcome to MCP.', response.structured_content[:message]
end
def test_output_schema_validation
response = GreetTool.call(
name: 'Test',
server_context: {}
)
assert response.structured_content.key?(:message)
assert response.structured_content.key?(:timestamp)
end
end
end
end
test/tools/calculate_tool_test.rb Template
# frozen_string_literal: true
require 'test_helper'
module MyMcpServer
module Tools
class CalculateToolTest < Minitest::Test
def test_addition
response = CalculateTool.call(
operation: 'add',
a: 5,
b: 3,
server_context: {}
)
refute response.is_error
assert_equal 8, response.structured_content[:result]
end
def test_subtraction
response = CalculateTool.call(
operation: 'subtract',
a: 10,
b: 4,
server_context: {}
)
refute response.is_error
assert_equal 6, response.structured_content[:result]
end
def test_multiplication
response = CalculateTool.call(
operation: 'multiply',
a: 6,
b: 7,
server_context: {}
)
refute response.is_error
assert_equal 42, response.structured_content[:result]
end
def test_division
response = CalculateTool.call(
operation: 'divide',
a: 15,
b: 3,
server_context: {}
)
refute response.is_error
assert_equal 5.0, response.structured_content[:result]
end
def test_division_by_zero
response = CalculateTool.call(
operation: 'divide',
a: 10,
b: 0,
server_context: {}
)
assert response.is_error
assert_match(/Division by zero/, response.content.first[:text])
end
def test_unknown_operation
response = CalculateTool.call(
operation: 'modulo',
a: 10,
b: 3,
server_context: {}
)
assert response.is_error
assert_match(/Unknown operation/, response.content.first[:text])
end
end
end
end
README.md Template
# My MCP Server
A Model Context Protocol server built with Ruby and the official MCP Ruby SDK.
## Features
- ✅ Tools: greet, calculate
- ✅ Prompts: code_review
- ✅ Resources: example-data
- ✅ Input/output schemas
- ✅ Tool annotations
- ✅ Structured content
- ✅ Full test coverage
## Requirements
- Ruby 3.0 or later
## Installation
```bash
bundle install
Usage
Stdio Transport
Run the server:
bundle exec bin/mcp-server
Then send JSON-RPC requests:
{"jsonrpc":"2.0","id":"1","method":"ping"}
{"jsonrpc":"2.0","id":"2","method":"tools/list"}
{"jsonrpc":"2.0","id":"3","method":"tools/call","params":{"name":"greet","arguments":{"name":"Ruby"}}}
Rails Integration
Add to your Rails controller:
class McpController < ApplicationController
def index
server = MyMcpServer::Server.new(
server_context: { user_id: current_user.id }
)
render json: server.handle_json(request.body.read)
end
end
Testing
Run tests:
bundle exec rake test
Run linter:
bundle exec rake rubocop
Run all checks:
bundle exec rake
Integration with Claude Desktop
Add to claude_desktop_config.json:
{
"mcpServers": {
"my-mcp-server": {
"command": "bundle",
"args": ["exec", "bin/mcp-server"],
"cwd": "/path/to/my-mcp-server"
}
}
}
Project Structure
my-mcp-server/
├── Gemfile # Dependencies
├── Rakefile # Build tasks
├── lib/ # Source code
│ ├── my_mcp_server.rb # Main entry point
│ └── my_mcp_server/ # Module namespace
│ ├── server.rb # Server setup
│ ├── tools/ # Tool implementations
│ ├── prompts/ # Prompt templates
│ └── resources/ # Resource handlers
├── bin/ # Executables
│ └── mcp-server # Stdio server
├── test/ # Test suite
│ ├── test_helper.rb # Test configuration
│ └── tools/ # Tool tests
└── README.md # This file
License
MIT
## Generation Instructions
1. **Ask for project name and description**
2. **Generate all files** with proper naming and module structure
3. **Use classes for tools and prompts** for better organization
4. **Include input/output schemas** for type safety
5. **Add tool annotations** for behavior hints
6. **Include structured content** in responses
7. **Implement comprehensive tests** for all tools
8. **Follow Ruby conventions** (snake_case, modules, frozen_string_literal)
9. **Add proper error handling** with is_error flag
10. **Provide both stdio and HTTP** usage examples