Add notification support

Co-authored-by: Kevin Fischer <kfischer_okarin@yahoo.co.jp>

lib/mcp/methods.rb

@@ -21,6 +21,11 @@ module MCP
 
     SAMPLING_CREATE_MESSAGE = "sampling/createMessage"
 
+    # Notification methods
+    NOTIFICATIONS_TOOLS_LIST_CHANGED = "notifications/tools/list_changed"
+    NOTIFICATIONS_PROMPTS_LIST_CHANGED = "notifications/prompts/list_changed"
+    NOTIFICATIONS_RESOURCES_LIST_CHANGED = "notifications/resources/list_changed"
+
     class MissingRequiredCapabilityError < StandardError
       attr_reader :method
       attr_reader :capability

lib/mcp/server.rb

@@ -98,6 +98,30 @@ module MCP
       @prompts[prompt.name_value] = prompt
     end
 
+    def notify_tools_list_changed
+      return unless @transport
+
+      @transport.send_notification(Methods::NOTIFICATIONS_TOOLS_LIST_CHANGED)
+    rescue => e
+      report_exception(e, { notification: "tools_list_changed" })
+    end
+
+    def notify_prompts_list_changed
+      return unless @transport
+
+      @transport.send_notification(Methods::NOTIFICATIONS_PROMPTS_LIST_CHANGED)
+    rescue => e
+      report_exception(e, { notification: "prompts_list_changed" })
+    end
+
+    def notify_resources_list_changed
+      return unless @transport
+
+      @transport.send_notification(Methods::NOTIFICATIONS_RESOURCES_LIST_CHANGED)
+    rescue => e
+      report_exception(e, { notification: "resources_list_changed" })
+    end
+
     def resources_list_handler(&block)
       @capabilities.support_resources
       @handlers[Methods::RESOURCES_LIST] = block

lib/mcp/server/transports/stdio_transport.rb

@@ -43,10 +43,18 @@ module MCP
           $stdout.flush
         end
 
-        def send_response(message)
-          json_message = message.is_a?(String) ? message : JSON.generate(message)
-          $stdout.puts(json_message)
-          $stdout.flush
+        def send_notification(method, params = nil)
+          notification = {
+            jsonrpc: "2.0",
+            method: method,
+          }
+          notification[:params] = params if params
+
+          send_response(notification)
+          true
+        rescue => e
+          MCP.configuration.exception_reporter.call(e, { error: "Failed to send notification" })
+          false
         end
       end
     end