diff --git a/core/src/main/java/com/google/adk/tools/mcp/McpAsyncToolset.java b/core/src/main/java/com/google/adk/tools/mcp/McpAsyncToolset.java
index 5e92410c9..45a2fe333 100644
--- a/core/src/main/java/com/google/adk/tools/mcp/McpAsyncToolset.java
+++ b/core/src/main/java/com/google/adk/tools/mcp/McpAsyncToolset.java
@@ -22,8 +22,8 @@
 import com.google.adk.tools.BaseTool;
 import com.google.adk.tools.BaseToolset;
 import com.google.adk.tools.NamedToolPredicate;
-import com.google.adk.tools.ToolPredicate;
 import com.google.common.collect.ImmutableList;
+import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import io.modelcontextprotocol.client.McpAsyncClient;
 import io.modelcontextprotocol.client.transport.ServerParameters;
 import io.reactivex.rxjava3.core.Flowable;
@@ -59,37 +59,42 @@ public class McpAsyncToolset implements BaseToolset {
 
   private final McpSessionManager mcpSessionManager;
   private final ObjectMapper objectMapper;
-  private final ToolPredicate toolFilter;
+  private final Optional<Object> toolFilter;
   private final AtomicReference<Mono<List<McpAsyncTool>>> mcpTools = new AtomicReference<>();
 
   /** Builder for McpAsyncToolset */
   public static class Builder {
     private Object connectionParams = null;
     private ObjectMapper objectMapper = null;
-    private ToolPredicate toolFilter = null;
+    private Optional<Object> toolFilter = null;
 
+    @CanIgnoreReturnValue
     public Builder connectionParams(ServerParameters connectionParams) {
       this.connectionParams = connectionParams;
       return this;
     }
 
+    @CanIgnoreReturnValue
     public Builder connectionParams(SseServerParameters connectionParams) {
       this.connectionParams = connectionParams;
       return this;
     }
 
+    @CanIgnoreReturnValue
     public Builder objectMapper(ObjectMapper objectMapper) {
       this.objectMapper = objectMapper;
       return this;
     }
 
-    public Builder toolFilter(ToolPredicate toolFilter) {
+    @CanIgnoreReturnValue
+    public Builder toolFilter(Optional<Object> toolFilter) {
       this.toolFilter = toolFilter;
       return this;
     }
 
+    @CanIgnoreReturnValue
     public Builder toolFilter(List<String> toolNames) {
-      this.toolFilter = new NamedToolPredicate(toolNames);
+      this.toolFilter = Optional.of(new NamedToolPredicate(toolNames));
       return this;
     }
 
@@ -97,9 +102,6 @@ public McpAsyncToolset build() {
       if (objectMapper == null) {
         objectMapper = JsonBaseModel.getMapper();
       }
-      if (toolFilter == null) {
-        toolFilter = (tool, context) -> true;
-      }
       if (connectionParams instanceof ServerParameters setSelectedParams) {
         return new McpAsyncToolset(setSelectedParams, objectMapper, toolFilter);
       } else if (connectionParams instanceof SseServerParameters sseServerParameters) {
@@ -116,11 +118,12 @@ public McpAsyncToolset build() {
    *
    * @param connectionParams The SSE connection parameters to the MCP server.
    * @param objectMapper An ObjectMapper instance for parsing schemas.
-   * @param toolFilter null or an implement for {@link ToolPredicate}, {@link
-   *     com.google.adk.tools.NamedToolPredicate}
+   * @param toolFilter An Optional containing either a ToolPredicate or a List of tool names.
    */
   public McpAsyncToolset(
-      SseServerParameters connectionParams, ObjectMapper objectMapper, ToolPredicate toolFilter) {
+      SseServerParameters connectionParams,
+      ObjectMapper objectMapper,
+      Optional<Object> toolFilter) {
     Objects.requireNonNull(connectionParams);
     Objects.requireNonNull(objectMapper);
     this.objectMapper = objectMapper;
@@ -133,11 +136,10 @@ public McpAsyncToolset(
    *
    * @param connectionParams The local server connection parameters to the MCP server.
    * @param objectMapper An ObjectMapper instance for parsing schemas.
-   * @param toolFilter null or an implement for {@link ToolPredicate}, {@link
-   *     com.google.adk.tools.NamedToolPredicate}
+   * @param toolFilter An Optional containing either a ToolPredicate or a List of tool names.
    */
   public McpAsyncToolset(
-      ServerParameters connectionParams, ObjectMapper objectMapper, ToolPredicate toolFilter) {
+      ServerParameters connectionParams, ObjectMapper objectMapper, Optional<Object> toolFilter) {
     Objects.requireNonNull(connectionParams);
     Objects.requireNonNull(objectMapper);
     this.objectMapper = objectMapper;
@@ -150,11 +152,10 @@ public McpAsyncToolset(
    *
    * @param mcpSessionManager The session manager for MCP connections.
    * @param objectMapper An ObjectMapper instance for parsing schemas.
-   * @param toolFilter null or an implement for {@link ToolPredicate}, {@link
-   *     com.google.adk.tools.NamedToolPredicate}
+   * @param toolFilter An Optional containing either a ToolPredicate or a List of tool names.
    */
   public McpAsyncToolset(
-      McpSessionManager mcpSessionManager, ObjectMapper objectMapper, ToolPredicate toolFilter) {
+      McpSessionManager mcpSessionManager, ObjectMapper objectMapper, Optional<Object> toolFilter) {
     Objects.requireNonNull(mcpSessionManager);
     Objects.requireNonNull(objectMapper);
     this.objectMapper = objectMapper;
@@ -171,10 +172,7 @@ public Flowable<BaseTool> getTools(ReadonlyContext readonlyContext) {
                 tools.stream()
                     .filter(
                         tool ->
-                            isToolSelected(
-                                tool,
-                                Optional.ofNullable(toolFilter),
-                                Optional.ofNullable(readonlyContext)))
+                            isToolSelected(tool, toolFilter, Optional.ofNullable(readonlyContext)))
                     .toList())
         .onErrorResumeNext(
             err -> {