implement BaseMetadata module mixin

Author: topherbullock

lib/mcp.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require_relative "mcp/base_metadata"
 require_relative "mcp/configuration"
 require_relative "mcp/content"
 require_relative "mcp/instrumentation"

lib/mcp/base_metadata.rb

@@ -0,0 +1,76 @@
+# frozen_string_literal: true
+
+module MCP
+  # Provides shared functionality for classes implementing the BaseMetadata interface from the MCP spec.
+  #
+  # BaseMetadata defines:
+  # - name: Intended for programmatic or logical use
+  # - title: Intended for UI and end-user contexts (optional)
+  #
+  # This module provides display_name logic that follows the spec:
+  # - Generally: use title if present, otherwise fall back to name
+  # - For Tool: use annotations.title first, then title, then name
+  module BaseMetadata
+    # Returns the appropriate display name according to spec priority.
+    #
+    # For most classes: title (if present) or name
+    # For Tool: annotations.title, title, or name
+    #
+    # @return [String] the display name
+    def display_name
+      if respond_to?(:annotations_value) && annotations_value&.title
+        annotations_value.title
+      elsif respond_to?(:title_value)
+        title_value || name_value
+      elsif respond_to?(:title)
+        title || name
+      else
+        name
+      end
+    end
+
+    # Module containing class-level methods for BaseMetadata.
+    # Use by including BaseMetadata and extending BaseMetadata::ClassMethods.
+    module ClassMethods
+      # Returns the appropriate display name according to spec priority.
+      #
+      # For Tool: annotations.title, title, or name
+      # For others: title or name
+      #
+      # @return [String] the display name
+      def display_name
+        if respond_to?(:annotations_value) && annotations_value&.title
+          annotations_value.title
+        elsif title_value
+          title_value
+        else
+          name_value
+        end
+      end
+
+      # Accessor for name value, must be implemented by including class
+      def name_value
+        raise NotImplementedError, "#{self} must implement name_value"
+      end
+
+      # Accessor for title value
+      def title_value
+        @title_value
+      end
+
+      # Class method to set or get title
+      # Note: Classes using this module should define their own NOT_SET constant
+      # which is used as a sentinel value to distinguish between getter and setter calls
+      #
+      # @param value [Object] the title value or NOT_SET to read
+      # @return [String, nil] the title value when reading
+      def title(value = NOT_SET)
+        if value == NOT_SET
+          @title_value
+        else
+          @title_value = value
+        end
+      end
+    end
+  end
+end

lib/mcp/prompt.rb

@@ -3,9 +3,10 @@
 module MCP
   class Prompt
     class << self
+      include BaseMetadata::ClassMethods
+
       NOT_SET = Object.new
 
-      attr_reader :title_value
       attr_reader :description_value
       attr_reader :arguments_value
       attr_reader :meta_value
@@ -45,14 +46,6 @@ def name_value
         @name_value || StringUtils.handle_from_class_name(name)
       end
 
-      def title(value = NOT_SET)
-        if value == NOT_SET
-          @title_value
-        else
-          @title_value = value
-        end
-      end
-
       def description(value = NOT_SET)
         if value == NOT_SET
           @description_value

lib/mcp/prompt/argument.rb

@@ -3,6 +3,8 @@
 module MCP
   class Prompt
     class Argument
+      include BaseMetadata
+
       attr_reader :name, :title, :description, :required
 
       def initialize(name:, title: nil, description: nil, required: false)

lib/mcp/resource.rb

@@ -2,6 +2,8 @@
 
 module MCP
   class Resource
+    include BaseMetadata
+
     attr_reader :uri, :name, :title, :description, :mime_type
 
     def initialize(uri:, name:, title: nil, description: nil, mime_type: nil)

lib/mcp/resource_template.rb

@@ -2,6 +2,8 @@
 
 module MCP
   class ResourceTemplate
+    include BaseMetadata
+
     attr_reader :uri_template, :name, :title, :description, :mime_type
 
     def initialize(uri_template:, name:, title: nil, description: nil, mime_type: nil)

lib/mcp/tool.rb

@@ -3,9 +3,10 @@
 module MCP
   class Tool
     class << self
+      include BaseMetadata::ClassMethods
+
       NOT_SET = Object.new
 
-      attr_reader :title_value
       attr_reader :description_value
       attr_reader :annotations_value
       attr_reader :meta_value
@@ -55,14 +56,6 @@ def input_schema_value
 
       attr_reader :output_schema_value
 
-      def title(value = NOT_SET)
-        if value == NOT_SET
-          @title_value
-        else
-          @title_value = value
-        end
-      end
-
       def description(value = NOT_SET)
         if value == NOT_SET
           @description_value

test/mcp/base_metadata_test.rb

@@ -0,0 +1,99 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class BaseMetadataTest < Minitest::Test
+  # Test instance-level BaseMetadata (Resource, ResourceTemplate, Prompt::Argument)
+  def test_resource_display_name_with_title
+    resource = MCP::Resource.new(uri: "file:///test", name: "test_resource", title: "Test Resource")
+    assert_equal("Test Resource", resource.display_name)
+  end
+
+  def test_resource_display_name_without_title
+    resource = MCP::Resource.new(uri: "file:///test", name: "test_resource")
+    assert_equal("test_resource", resource.display_name)
+  end
+
+  def test_resource_template_display_name_with_title
+    template = MCP::ResourceTemplate.new(uri_template: "file:///{name}", name: "test_template", title: "Test Template")
+    assert_equal("Test Template", template.display_name)
+  end
+
+  def test_resource_template_display_name_without_title
+    template = MCP::ResourceTemplate.new(uri_template: "file:///{name}", name: "test_template")
+    assert_equal("test_template", template.display_name)
+  end
+
+  def test_prompt_argument_display_name_with_title
+    argument = MCP::Prompt::Argument.new(name: "test_arg", title: "Test Argument")
+    assert_equal("Test Argument", argument.display_name)
+  end
+
+  def test_prompt_argument_display_name_without_title
+    argument = MCP::Prompt::Argument.new(name: "test_arg")
+    assert_equal("test_arg", argument.display_name)
+  end
+
+  # Test class-level BaseMetadata (Tool, Prompt)
+  def test_tool_display_name_with_annotations_title
+    tool_class = Class.new(MCP::Tool) do
+      tool_name "test_tool"
+      title "Tool Title"
+      annotations(title: "Annotations Title")
+    end
+
+    assert_equal("Annotations Title", tool_class.display_name)
+  end
+
+  def test_tool_display_name_with_title_only
+    tool_class = Class.new(MCP::Tool) do
+      tool_name "test_tool"
+      title "Tool Title"
+    end
+
+    assert_equal("Tool Title", tool_class.display_name)
+  end
+
+  def test_tool_display_name_with_name_only
+    tool_class = Class.new(MCP::Tool) do
+      tool_name "test_tool"
+    end
+
+    assert_equal("test_tool", tool_class.display_name)
+  end
+
+  def test_prompt_display_name_with_title
+    prompt_class = Class.new(MCP::Prompt) do
+      prompt_name "test_prompt"
+      title "Prompt Title"
+    end
+
+    assert_equal("Prompt Title", prompt_class.display_name)
+  end
+
+  def test_prompt_display_name_without_title
+    prompt_class = Class.new(MCP::Prompt) do
+      prompt_name "test_prompt"
+    end
+
+    assert_equal("test_prompt", prompt_class.display_name)
+  end
+
+  def test_title_method_still_works_on_tool
+    tool_class = Class.new(MCP::Tool) do
+      tool_name "test_tool"
+      title "My Tool"
+    end
+
+    assert_equal("My Tool", tool_class.title)
+  end
+
+  def test_title_method_still_works_on_prompt
+    prompt_class = Class.new(MCP::Prompt) do
+      prompt_name "test_prompt"
+      title "My Prompt"
+    end
+
+    assert_equal("My Prompt", prompt_class.title)
+  end
+end