Update core/src/main/java/com/google/adk/tools/AgentTool.java

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: voborl00

core/src/main/java/com/google/adk/tools/AgentTool.java

@@ -71,10 +71,10 @@ public static AgentTool create(BaseAgent agent) {
   protected AgentTool(
       BaseAgent agent,
       boolean skipSummarization,
-      BaseSessionService sessionService,
-      BaseArtifactService artifactService,
-      BaseMemoryService memoryService,
-      List<BasePlugin> plugins) {
+      @org.jspecify.annotations.Nullable BaseSessionService sessionService,
+      @org.jspecify.annotations.Nullable BaseArtifactService artifactService,
+      @org.jspecify.annotations.Nullable BaseMemoryService memoryService,
+      @org.jspecify.annotations.Nullable List<BasePlugin> plugins) {
     super(agent.name(), agent.description());
     this.agent = agent;
     this.skipSummarization = skipSummarization;