[fit] add notification/tools/list_changed method in MCP server

Author: CodeCasterX

framework/fel/java/plugins/tool-mcp-server/src/main/java/modelengine/fel/tool/mcp/server/McpController.java

@@ -48,14 +48,15 @@
  * @since 2025-05-13
  */
 @Component
-public class McpController {
+public class McpController implements McpServer.ToolsChangedObserver {
     private static final Logger log = Logger.get(McpController.class);
     private static final String MESSAGE_PATH = "/mcp/message";
     private static final String EVENT_ENDPOINT = "endpoint";
     private static final String EVENT_MESSAGE = "message";
     private static final String METHOD_INITIALIZE = "initialize";
     private static final String METHOD_TOOLS_LIST = "tools/list";
     private static final String METHOD_TOOLS_CALL = "tools/call";
+    private static final String METHOD_NOTIFICATION_TOOLS_CHANGED = "notifications/tools/list_changed";
     private static final String RESPONSE_OK = StringUtils.EMPTY;
 
     private final Map<String, Emitter<TextEvent>> emitters = new ConcurrentHashMap<>();
@@ -79,6 +80,7 @@ public McpController(@Value("${base-url}") String baseUrl, @Fit(alias = "json")
         this.baseUrl = notBlank(baseUrl, "The base URL for MCP server cannot be blank.");
         this.serializer = notNull(serializer, "The json serializer cannot be null.");
         notNull(mcpServer, "The MCP server cannot be null.");
+        mcpServer.registerToolsChangedObserver(this);
 
         this.methodHandlers.put(METHOD_INITIALIZE, new InitializeHandler(mcpServer));
         this.methodHandlers.put(METHOD_TOOLS_LIST, new ToolListHandler(mcpServer));
@@ -170,4 +172,16 @@ public Object receiveMcpMessage(@RequestQuery(name = "sessionId") String session
         log.info("Send MCP message. [response={}]", serialized);
         return RESPONSE_OK;
     }
+
+    @Override
+    public void onToolsChanged() {
+        JsonRpcEntity notification = new JsonRpcEntity();
+        notification.setMethod(METHOD_NOTIFICATION_TOOLS_CHANGED);
+        String serialized = this.serializer.serialize(notification);
+        this.emitters.forEach((sessionId, emitter) -> {
+            TextEvent textEvent = TextEvent.custom().id(sessionId).event(EVENT_MESSAGE).data(serialized).build();
+            emitter.emit(textEvent);
+            log.info("Send MCP notification: tools changed. [sessionId={}]", sessionId);
+        });
+    }
 }

framework/fel/java/plugins/tool-mcp-server/src/main/java/modelengine/fel/tool/mcp/server/McpServer.java

@@ -40,4 +40,21 @@ public interface McpServer {
      * @return The tool result as a {@link Object}.
      */
     Object callTool(String name, Map<String, Object> arguments);
+
+    /**
+     * Registers MCP Server Tools Changed Observer.
+     *
+     * @param observer The MCP Server Tools Changed Observer as a {@link ToolsChangedObserver}.
+     */
+    void registerToolsChangedObserver(ToolsChangedObserver observer);
+
+    /**
+     * Represents the MCP Server Tools Changed Observer.
+     */
+    interface ToolsChangedObserver {
+        /**
+         * Called when MCP Server Tools changed.
+         */
+        void onToolsChanged();
+    }
 }

framework/fel/java/plugins/tool-mcp-server/src/main/java/modelengine/fel/tool/mcp/server/support/DefaultMcpServer.java

@@ -18,6 +18,7 @@
 import modelengine.fitframework.util.MapUtils;
 import modelengine.fitframework.util.StringUtils;
 
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
@@ -34,6 +35,7 @@ public class DefaultMcpServer implements McpServer, ToolChangedObserver {
 
     private final ToolExecuteService toolExecuteService;
     private final Map<String, ToolEntity> tools = new ConcurrentHashMap<>();
+    private final List<ToolsChangedObserver> toolsChangedObservers = new ArrayList<>();
 
     /**
      * Constructs a new instance of the DefaultMcpServer class.
@@ -72,6 +74,13 @@ public Object callTool(String name, Map<String, Object> arguments) {
         return result;
     }
 
+    @Override
+    public void registerToolsChangedObserver(ToolsChangedObserver observer) {
+        if (observer != null) {
+            this.toolsChangedObservers.add(observer);
+        }
+    }
+
     @Override
     public void onToolAdded(String name, String description, Map<String, Object> schema) {
         if (StringUtils.isBlank(name)) {
@@ -92,6 +101,7 @@ public void onToolAdded(String name, String description, Map<String, Object> sch
         tool.setInputSchema(schema);
         this.tools.put(name, tool);
         log.info("Tool added to MCP server. [toolName={}, description={}, schema={}]", name, description, schema);
+        this.toolsChangedObservers.forEach(ToolsChangedObserver::onToolsChanged);
     }
 
     @Override
@@ -102,5 +112,6 @@ public void onToolRemoved(String name) {
         }
         this.tools.remove(name);
         log.info("Tool removed from MCP server. [toolName={}]", name);
+        this.toolsChangedObservers.forEach(ToolsChangedObserver::onToolsChanged);
     }
 }