refactor: Replacing Optional in BaseToolSet with Nullable

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

@@ -20,6 +20,7 @@
 import io.reactivex.rxjava3.core.Flowable;
 import java.util.List;
 import java.util.Optional;
+import javax.annotation.Nullable;
 
 /** Base interface for toolsets. */
 public interface BaseToolset extends AutoCloseable {
@@ -43,28 +44,35 @@ public interface BaseToolset extends AutoCloseable {
   void close() throws Exception;
 
   /**
-   * Helper method to be used by implementers that returns true if the given tool is in the provided
-   * list of tools of if testing against the given ToolPredicate returns true (otherwise false).
+   * Checks if a tool should be selected based on a filter.
    *
    * @param tool The tool to check.
-   * @param toolFilter An Optional containing either a ToolPredicate or a List of tool names.
-   * @param readonlyContext The current context.
-   * @return true if the tool is selected.
+   * @param toolFilter A ToolPredicate, a List of tool names, or null.
+   * @param readonlyContext The context for checking the tool, or null.
    */
   default boolean isToolSelected(
-      BaseTool tool, Optional<Object> toolFilter, Optional<ReadonlyContext> readonlyContext) {
-    if (toolFilter.isEmpty()) {
+      BaseTool tool, @Nullable Object toolFilter, @Nullable ReadonlyContext readonlyContext) {
+    if (toolFilter == null) {
       return true;
     }
-    Object filter = toolFilter.get();
-    if (filter instanceof ToolPredicate toolPredicate) {
+
+    if (toolFilter instanceof ToolPredicate toolPredicate) {
       return toolPredicate.test(tool, readonlyContext);
     }
-    if (filter instanceof List) {
-      @SuppressWarnings("unchecked")
-      List<String> toolNames = (List<String>) filter;
+
+    if (toolFilter instanceof List<?> toolNames) {
       return toolNames.contains(tool.name());
     }
+
     return false;
   }
+
+  /**
+   * @deprecated Use {@link #isToolSelected(BaseTool, Object, ReadonlyContext)} instead.
+   */
+  @Deprecated
+  default boolean isToolSelected(
+      BaseTool tool, Optional<Object> toolFilter, Optional<ReadonlyContext> readonlyContext) {
+    return isToolSelected(tool, toolFilter.orElse(null), readonlyContext.orElse(null));
+  }
 }

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

@@ -18,6 +18,7 @@
 
 import com.google.adk.agents.ReadonlyContext;
 import java.util.Optional;
+import javax.annotation.Nullable;
 
 /**
  * Functional interface to decide whether a tool should be exposed to the LLM based on the current
@@ -31,6 +32,19 @@ public interface ToolPredicate {
    * @param tool The tool to check.
    * @param readonlyContext The current context.
    * @return true if the tool should be selected, false otherwise.
+   * @deprecated Use {@link #test(BaseTool, ReadonlyContext)} instead.
    */
+  @Deprecated
   boolean test(BaseTool tool, Optional<ReadonlyContext> readonlyContext);
+
+  /**
+   * Decides if the given tool is selected.
+   *
+   * @param tool The tool to check.
+   * @param readonlyContext The current context.
+   * @return true if the tool should be selected, false otherwise.
+   */
+  default boolean test(BaseTool tool, @Nullable ReadonlyContext readonlyContext) {
+    return test(tool, Optional.ofNullable(readonlyContext));
+  }
 }

core/src/main/java/com/google/adk/tools/mcp/McpAsyncToolset.java

@@ -170,9 +170,7 @@ public Flowable<BaseTool> getTools(ReadonlyContext readonlyContext) {
         .map(
             tools ->
                 tools.stream()
-                    .filter(
-                        tool ->
-                            isToolSelected(tool, toolFilter, Optional.ofNullable(readonlyContext)))
+                    .filter(tool -> isToolSelected(tool, toolFilter.orElse(null), readonlyContext))
                     .toList())
         .onErrorResumeNext(
             err -> {

core/src/main/java/com/google/adk/tools/mcp/McpToolset.java

@@ -216,9 +216,7 @@ public Flowable<BaseTool> getTools(ReadonlyContext readonlyContext) {
                               new McpTool(
                                   tool, this.mcpSession, this.mcpSessionManager, this.objectMapper))
                       .filter(
-                          tool ->
-                              isToolSelected(
-                                  tool, toolFilter, Optional.ofNullable(readonlyContext))));
+                          tool -> isToolSelected(tool, toolFilter.orElse(null), readonlyContext)));
             })
         .retryWhen(
             errorObservable ->