Support Ruby 2.7 - Ruby 3.1

.github/workflows/ci.yml

@@ -7,6 +7,9 @@ jobs:
     strategy:
       matrix:
         entry:
+          - { ruby: '2.7', allowed-failure: false }
+          - { ruby: '3.0', allowed-failure: false }
+          - { ruby: '3.1', allowed-failure: false }
           - { ruby: '3.2', allowed-failure: false }
           - { ruby: '3.3', allowed-failure: false }
           - { ruby: '3.4', allowed-failure: false }
@@ -29,7 +32,7 @@ jobs:
       - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 3.2 # Specify the oldest supported Ruby version.
+          ruby-version: 4.0 # Specify the latest supported Ruby version.
           bundler-cache: true
       - run: bundle exec rake rubocop
 
@@ -40,6 +43,6 @@ jobs:
       - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 3.2 # Specify the oldest supported Ruby version.
+          ruby-version: 4.0 # Specify the latest supported Ruby version.
           bundler-cache: true
       - run: bundle exec yard --no-output

.rubocop.yml

@@ -5,6 +5,9 @@ plugins:
   - rubocop-minitest
   - rubocop-rake
 
+AllCops:
+  TargetRubyVersion: 2.7
+
 Gemspec/DevelopmentDependencies:
   Enabled: true
 

AGENTS.md

@@ -6,7 +6,7 @@ This is the official Ruby SDK for the Model Context Protocol (MCP), implementing
 
 ## Dev environment setup
 
-- Ruby 3.2.0+ required
+- Ruby 3.2.0+ required to run the full test suite, including all Sorbet-related features
 - Run `bundle install` to install dependencies
 - Dependencies: `json-schema` >= 4.1 - Schema validation
 

Gemfile

@@ -8,17 +8,18 @@ gemspec
 # Specify development dependencies below
 gem "rubocop-minitest", require: false
 gem "rubocop-rake", require: false
-gem "rubocop-shopify", require: false
+gem "rubocop-shopify", ">= 2.18", require: false if RUBY_VERSION >= "3.1"
 
 gem "puma", ">= 5.0.0"
 gem "rackup", ">= 2.1.0"
 
 gem "activesupport"
-gem "debug"
+# Fix io-console install error when Ruby 3.0.
+gem "debug" if RUBY_VERSION >= "3.1"
 gem "rake", "~> 13.0"
-gem "sorbet-static-and-runtime"
+gem "sorbet-static-and-runtime" if RUBY_VERSION >= "3.0"
 gem "yard", "~> 0.9"
-gem "yard-sorbet", "~> 0.9"
+gem "yard-sorbet", "~> 0.9" if RUBY_VERSION >= "3.1"
 
 group :test do
   gem "faraday", ">= 2.0"

lib/json_rpc_handler.rb

@@ -22,14 +22,14 @@ class ErrorCode
 
   def handle(request, id_validation_pattern: DEFAULT_ALLOWED_ID_CHARACTERS, &method_finder)
     if request.is_a?(Array)
-      return error_response(id: :unknown_id, id_validation_pattern:, error: {
+      return error_response(id: :unknown_id, id_validation_pattern: id_validation_pattern, error: {
         code: ErrorCode::INVALID_REQUEST,
         message: "Invalid Request",
         data: "Request is an empty array",
       }) if request.empty?
 
       # Handle batch requests
-      responses = request.map { |req| process_request(req, id_validation_pattern:, &method_finder) }.compact
+      responses = request.map { |req| process_request(req, id_validation_pattern: id_validation_pattern, &method_finder) }.compact
 
       # A single item is hoisted out of the array
       return responses.first if responses.one?
@@ -38,9 +38,9 @@ def handle(request, id_validation_pattern: DEFAULT_ALLOWED_ID_CHARACTERS, &metho
       responses if responses.any?
     elsif request.is_a?(Hash)
       # Handle single request
-      process_request(request, id_validation_pattern:, &method_finder)
+      process_request(request, id_validation_pattern: id_validation_pattern, &method_finder)
     else
-      error_response(id: :unknown_id, id_validation_pattern:, error: {
+      error_response(id: :unknown_id, id_validation_pattern: id_validation_pattern, error: {
         code: ErrorCode::INVALID_REQUEST,
         message: "Invalid Request",
         data: "Request must be an array or a hash",
@@ -51,9 +51,9 @@ def handle(request, id_validation_pattern: DEFAULT_ALLOWED_ID_CHARACTERS, &metho
   def handle_json(request_json, id_validation_pattern: DEFAULT_ALLOWED_ID_CHARACTERS, &method_finder)
     begin
       request = JSON.parse(request_json, symbolize_names: true)
-      response = handle(request, id_validation_pattern:, &method_finder)
+      response = handle(request, id_validation_pattern: id_validation_pattern, &method_finder)
     rescue JSON::ParserError
-      response = error_response(id: :unknown_id, id_validation_pattern:, error: {
+      response = error_response(id: :unknown_id, id_validation_pattern: id_validation_pattern, error: {
         code: ErrorCode::PARSE_ERROR,
         message: "Parse error",
         data: "Invalid JSON",
@@ -74,7 +74,7 @@ def process_request(request, id_validation_pattern:, &method_finder)
       'Method name must be a string and not start with "rpc."'
     end
 
-    return error_response(id: :unknown_id, id_validation_pattern:, error: {
+    return error_response(id: :unknown_id, id_validation_pattern: id_validation_pattern, error: {
       code: ErrorCode::INVALID_REQUEST,
       message: "Invalid Request",
       data: error,
@@ -84,7 +84,7 @@ def process_request(request, id_validation_pattern:, &method_finder)
     params = request[:params]
 
     unless valid_params?(params)
-      return error_response(id:, id_validation_pattern:, error: {
+      return error_response(id: id, id_validation_pattern: id_validation_pattern, error: {
         code: ErrorCode::INVALID_PARAMS,
         message: "Invalid params",
         data: "Method parameters must be an array or an object or null",
@@ -95,7 +95,7 @@ def process_request(request, id_validation_pattern:, &method_finder)
       method = method_finder.call(method_name)
 
       if method.nil?
-        return error_response(id:, id_validation_pattern:, error: {
+        return error_response(id: id, id_validation_pattern: id_validation_pattern, error: {
           code: ErrorCode::METHOD_NOT_FOUND,
           message: "Method not found",
           data: method_name,
@@ -104,9 +104,9 @@ def process_request(request, id_validation_pattern:, &method_finder)
 
       result = method.call(params)
 
-      success_response(id:, result:)
+      success_response(id: id, result: result)
     rescue StandardError => e
-      error_response(id:, id_validation_pattern:, error: {
+      error_response(id: id, id_validation_pattern: id_validation_pattern, error: {
         code: ErrorCode::INTERNAL_ERROR,
         message: "Internal error",
         data: e.message,
@@ -136,8 +136,8 @@ def valid_params?(params)
   def success_response(id:, result:)
     {
       jsonrpc: Version::V2_0,
-      id:,
-      result:,
+      id: id,
+      result: result,
     } unless id.nil?
   end
 

lib/mcp/client/http.rb

@@ -18,42 +18,42 @@ def send_request(request:)
       rescue Faraday::BadRequestError => e
         raise RequestHandlerError.new(
           "The #{method} request is invalid",
-          { method:, params: },
+          { method: method, params: params },
           error_type: :bad_request,
           original_error: e,
         )
       rescue Faraday::UnauthorizedError => e
         raise RequestHandlerError.new(
           "You are unauthorized to make #{method} requests",
-          { method:, params: },
+          { method: method, params: params },
           error_type: :unauthorized,
           original_error: e,
         )
       rescue Faraday::ForbiddenError => e
         raise RequestHandlerError.new(
           "You are forbidden to make #{method} requests",
-          { method:, params: },
+          { method: method, params: params },
           error_type: :forbidden,
           original_error: e,
         )
       rescue Faraday::ResourceNotFound => e
         raise RequestHandlerError.new(
           "The #{method} request is not found",
-          { method:, params: },
+          { method: method, params: params },
           error_type: :not_found,
           original_error: e,
         )
       rescue Faraday::UnprocessableEntityError => e
         raise RequestHandlerError.new(
           "The #{method} request is unprocessable",
-          { method:, params: },
+          { method: method, params: params },
           error_type: :unprocessable_entity,
           original_error: e,
         )
       rescue Faraday::Error => e # Catch-all
         raise RequestHandlerError.new(
           "Internal error handling #{method} request",
-          { method:, params: },
+          { method: method, params: params },
           error_type: :internal_error,
           original_error: e,
         )

lib/mcp/configuration.rb

@@ -85,10 +85,10 @@ def merge(other)
       validate_tool_call_arguments = other.validate_tool_call_arguments
 
       Configuration.new(
-        exception_reporter:,
-        instrumentation_callback:,
-        protocol_version:,
-        validate_tool_call_arguments:,
+        exception_reporter: exception_reporter,
+        instrumentation_callback: instrumentation_callback,
+        protocol_version: protocol_version,
+        validate_tool_call_arguments: validate_tool_call_arguments,
       )
     end
 

lib/mcp/content.rb

@@ -11,7 +11,7 @@ def initialize(text, annotations: nil)
       end
 
       def to_h
-        { text:, annotations:, type: "text" }.compact
+        { text: text, annotations: annotations, type: "text" }.compact
       end
     end
 
@@ -25,7 +25,7 @@ def initialize(data, mime_type, annotations: nil)
       end
 
       def to_h
-        { data:, mime_type:, annotations:, type: "image" }.compact
+        { data: data, mime_type: mime_type, annotations: annotations, type: "image" }.compact
       end
     end
   end

lib/mcp/instrumentation.rb

@@ -6,7 +6,7 @@ def instrument_call(method, &block)
       start_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)
       begin
         @instrumentation_data = {}
-        add_instrumentation_data(method:)
+        add_instrumentation_data(method: method)
 
         result = yield block
 

lib/mcp/prompt.rb

@@ -96,7 +96,7 @@ def define(name: nil, title: nil, description: nil, icons: [], arguments: [], me
           icons icons
           arguments arguments
           define_singleton_method(:template) do |args, server_context: nil|
-            instance_exec(args, server_context:, &block)
+            instance_exec(args, server_context: server_context, &block)
           end
           meta meta
         end

lib/mcp/prompt/message.rb

@@ -11,7 +11,7 @@ def initialize(role:, content:)
       end
 
       def to_h
-        { role:, content: content.to_h }.compact
+        { role: role, content: content.to_h }.compact
       end
     end
   end

lib/mcp/prompt/result.rb

@@ -11,7 +11,7 @@ def initialize(description: nil, messages: [])
       end
 
       def to_h
-        { description:, messages: messages.map(&:to_h) }.compact
+        { description: description, messages: messages.map(&:to_h) }.compact
       end
     end
   end

lib/mcp/resource/contents.rb

@@ -11,7 +11,7 @@ def initialize(uri:, mime_type: nil)
       end
 
       def to_h
-        { uri:, mime_type: }.compact
+        { uri: uri, mime_type: mime_type }.compact
       end
     end
 

lib/mcp/resource/embedded.rb

@@ -10,7 +10,7 @@ def initialize(resource:, annotations: nil)
       end
 
       def to_h
-        { resource: resource.to_h, annotations: }.compact
+        { resource: resource.to_h, annotations: annotations }.compact
       end
     end
   end

lib/mcp/server.rb

@@ -114,7 +114,7 @@ def handle_json(request)
     end
 
     def define_tool(name: nil, title: nil, description: nil, input_schema: nil, annotations: nil, meta: nil, &block)
-      tool = Tool.define(name:, title:, description:, input_schema:, annotations:, meta:, &block)
+      tool = Tool.define(name: name, title: title, description: description, input_schema: input_schema, annotations: annotations, meta: meta, &block)
       tool_name = tool.name_value
 
       @tool_names << tool_name
@@ -124,7 +124,7 @@ def define_tool(name: nil, title: nil, description: nil, input_schema: nil, anno
     end
 
     def define_prompt(name: nil, title: nil, description: nil, arguments: [], &block)
-      prompt = Prompt.define(name:, title:, description:, arguments:, &block)
+      prompt = Prompt.define(name: name, title: title, description: description, arguments: arguments, &block)
       @prompts[prompt.name_value] = prompt
 
       validate!
@@ -289,11 +289,11 @@ def default_capabilities
 
     def server_info
       @server_info ||= {
-        description:,
-        icons:,
-        name:,
-        title:,
-        version:,
+        description: description,
+        icons: icons,
+        name: name,
+        title: title,
+        version: version,
         websiteUrl: website_url,
       }.compact
     end
@@ -316,13 +316,13 @@ def call_tool(request)
 
       tool = tools[tool_name]
       unless tool
-        add_instrumentation_data(tool_name:, error: :tool_not_found)
+        add_instrumentation_data(tool_name: tool_name, error: :tool_not_found)
 
         return error_tool_response("Tool not found: #{tool_name}")
       end
 
       arguments = request[:arguments] || {}
-      add_instrumentation_data(tool_name:)
+      add_instrumentation_data(tool_name: tool_name)
 
       if tool.input_schema&.missing_required_arguments?(arguments)
         add_instrumentation_data(error: :missing_required_arguments)
@@ -360,7 +360,7 @@ def get_prompt(request)
         raise RequestHandlerError.new("Prompt not found #{prompt_name}", request, error_type: :prompt_not_found)
       end
 
-      add_instrumentation_data(prompt_name:)
+      add_instrumentation_data(prompt_name: prompt_name)
 
       prompt_args = request[:arguments]
       prompt.validate_arguments!(prompt_args)

lib/mcp/server/transports/streamable_http_transport.rb

@@ -42,7 +42,7 @@ def send_notification(method, params = nil, session_id: nil)
 
           notification = {
             jsonrpc: "2.0",
-            method:,
+            method: method,
           }
           notification[:params] = params if params
 

lib/mcp/tool/annotations.rb

@@ -19,7 +19,7 @@ def to_h
           idempotentHint: idempotent_hint,
           openWorldHint: open_world_hint,
           readOnlyHint: read_only_hint,
-          title:,
+          title: title,
         }.compact
       end
     end

lib/mcp/tool/response.rb

@@ -23,7 +23,7 @@ def error?
       end
 
       def to_h
-        { content:, isError: error?, structuredContent: @structured_content }.compact
+        { content: content, isError: error?, structuredContent: @structured_content }.compact
       end
     end
   end

mcp.gemspec

@@ -13,7 +13,8 @@ Gem::Specification.new do |spec|
   spec.homepage      = "https://github.com/modelcontextprotocol/ruby-sdk"
   spec.license       = "MIT"
 
-  spec.required_ruby_version = ">= 3.2.0"
+  # Since this library is used by a broad range of users, it does not align its support policy with Ruby's EOL.
+  spec.required_ruby_version = ">= 2.7.0"
 
   spec.metadata["allowed_push_host"] = "https://rubygems.org"
   spec.metadata["changelog_uri"] = "https://github.com/modelcontextprotocol/ruby-sdk/releases/tag/v#{spec.version}"