Allow stable protocol specification version "2025-11-25"

The MCP specification dated 2025-11-25 has been released:

- https://modelcontextprotocol.io/specification/2025-11-25
- https://blog.modelcontextprotocol.io/posts/2025-11-25-first-mcp-anniversary

This PR allows `'2025-11-25'` to be specified for the `:protocol_version` keyword argument
in `MCP::Configuration.new`.

Author: koic

README.md

@@ -173,7 +173,7 @@ class ApplicationController < ActionController::Base
   def index
     server = MCP::Server.new(
       name: "my_server",
-      title: "Example Server Display Name", # WARNING: This is a `Draft` and is not supported in the `Version 2025-06-18 (latest)` specification.
+      title: "Example Server Display Name",
       version: "1.0.0",
       instructions: "Use the tools of this server as a last resort",
       tools: [SomeTool, AnotherTool],
@@ -391,7 +391,7 @@ This gem provides a `MCP::Tool` class that can be used to create tools in three
 
 ```ruby
 class MyTool < MCP::Tool
-  title "My Tool" # WARNING: This is a `Draft` and is not supported in the `Version 2025-06-18 (latest)` specification.
+  title "My Tool"
   description "This tool performs specific functionality..."
   input_schema(
     properties: {
@@ -428,7 +428,7 @@ tool = MyTool
 ```ruby
 tool = MCP::Tool.define(
   name: "my_tool",
-  title: "My Tool", # WARNING: This is a `Draft` and is not supported in the `Version 2025-06-18 (latest)` specification.
+  title: "My Tool",
   description: "This tool performs specific functionality...",
   annotations: {
     read_only_hint: true,
@@ -633,7 +633,7 @@ The `MCP::Prompt` class provides three ways to create prompts:
 ```ruby
 class MyPrompt < MCP::Prompt
   prompt_name "my_prompt"  # Optional - defaults to underscored class name
-  title "My Prompt" # WARNING: This is a `Draft` and is not supported in the `Version 2025-06-18 (latest)` specification.
+  title "My Prompt"
   description "This prompt performs specific functionality..."
   arguments [
     MCP::Prompt::Argument.new(
@@ -672,7 +672,7 @@ prompt = MyPrompt
 ```ruby
 prompt = MCP::Prompt.define(
   name: "my_prompt",
-  title: "My Prompt", # WARNING: This is a `Draft` and is not supported in the `Version 2025-06-18 (latest)` specification.
+  title: "My Prompt",
   description: "This prompt performs specific functionality...",
   arguments: [
     MCP::Prompt::Argument.new(
@@ -797,7 +797,7 @@ The `MCP::Resource` class provides a way to register resources with the server.
 resource = MCP::Resource.new(
   uri: "https://example.com/my_resource",
   name: "my-resource",
-  title: "My Resource", # WARNING: This is a `Draft` and is not supported in the `Version 2025-06-18 (latest)` specification.
+  title: "My Resource",
   description: "Lorem ipsum dolor sit amet",
   mime_type: "text/html",
 )
@@ -830,7 +830,7 @@ The `MCP::ResourceTemplate` class provides a way to register resource templates
 resource_template = MCP::ResourceTemplate.new(
   uri_template: "https://example.com/my_resource_template",
   name: "my-resource-template",
-  title: "My Resource Template", # WARNING: This is a `Draft` and is not supported in the `Version 2025-06-18 (latest)` specification.
+  title: "My Resource Template",
   description: "Lorem ipsum dolor sit amet",
   mime_type: "text/html",
 )

lib/mcp/configuration.rb

@@ -5,7 +5,7 @@ class Configuration
     # DRAFT-2025-v3 is the latest draft protocol version:
     # https://github.com/modelcontextprotocol/modelcontextprotocol/blob/14ec41c/schema/draft/schema.ts#L15
     DRAFT_PROTOCOL_VERSION = "DRAFT-2025-v3"
-    SUPPORTED_STABLE_PROTOCOL_VERSIONS = ["2025-06-18", "2025-03-26", "2024-11-05"]
+    SUPPORTED_STABLE_PROTOCOL_VERSIONS = ["2025-11-25", "2025-06-18", "2025-03-26", "2024-11-05"]
 
     attr_writer :exception_reporter, :instrumentation_callback
 

lib/mcp/server.rb

@@ -174,7 +174,7 @@ def prompts_get_handler(&block)
     private
 
     def validate!
-      # NOTE: The draft protocol version is the next version after 2025-03-26.
+      # NOTE: The draft protocol version is the next version after 2025-11-25.
       if @configuration.protocol_version <= "2025-03-26"
         if server_info.key?(:title)
           message = "Error occurred in server_info. `title` is not supported in protocol version 2025-03-26 or earlier"

test/mcp/configuration_test.rb

@@ -52,7 +52,7 @@ class ConfigurationTest < ActiveSupport::TestCase
         Configuration.new(protocol_version: Configuration::DRAFT_PROTOCOL_VERSION)
       end
 
-      assert_equal("protocol_version must be 2025-06-18, 2025-03-26, or 2024-11-05", exception.message)
+      assert_equal("protocol_version must be 2025-11-25, 2025-06-18, 2025-03-26, or 2024-11-05", exception.message)
     end
 
     test "raises ArgumentError when protocol_version is not a supported protocol version" do
@@ -61,7 +61,7 @@ class ConfigurationTest < ActiveSupport::TestCase
         custom_version = "2025-03-27"
         config.protocol_version = custom_version
       end
-      assert_equal("protocol_version must be 2025-06-18, 2025-03-26, or 2024-11-05", exception.message)
+      assert_equal("protocol_version must be 2025-11-25, 2025-06-18, 2025-03-26, or 2024-11-05", exception.message)
     end
 
     test "raises ArgumentError when protocol_version is not a boolean value" do