Add deprecation and single predicate

Author: pusewicz

lib/mcp/tool/response.rb

@@ -3,18 +3,27 @@
 module MCP
   class Tool
     class Response
-      attr_reader :content, :error
+      NOT_GIVEN = Object.new.freeze
+
+      attr_reader :content
+
+      def initialize(content, deprecated_error = NOT_GIVEN, error: false)
+        if deprecated_error != NOT_GIVEN
+          warn("Passing `error` with the 2nd argument of `Response.new` is deprecated. Use keyword argument like `Response.new(content, error: error)` instead.", uplevel: 1)
+          error = deprecated_error
+        end
 
-      def initialize(content, error: false)
         @content = content
         @error = error
       end
 
+      def error?
+        !!@error
+      end
+
       def to_h
         { content:, isError: error? }.compact
       end
-
-      alias_method :error?, :error
     end
   end
 end