fix: add schema validation to SetModelResponseTool

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

@@ -16,6 +16,7 @@
 
 package com.google.adk.tools;
 
+import com.google.adk.SchemaUtils;
 import com.google.genai.types.FunctionDeclaration;
 import com.google.genai.types.Schema;
 import io.reactivex.rxjava3.core.Single;
@@ -58,6 +59,10 @@ public Optional<FunctionDeclaration> declaration() {
   public Single<Map<String, Object>> runAsync(Map<String, Object> args, ToolContext toolContext) {
     // This tool is a marker for the final response, it doesn't do anything but return its arguments
     // which will be captured as the final result.
-    return Single.just(args);
+    return Single.fromCallable(
+        () -> {
+          SchemaUtils.validateMapOnSchema(args, outputSchema, /* isInput= */ false);
+          return args;
+        });
   }
 }

core/src/test/java/com/google/adk/tools/SetModelResponseToolTest.java

@@ -0,0 +1,123 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.adk.tools;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.assertThrows;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.genai.types.FunctionDeclaration;
+import com.google.genai.types.Schema;
+import java.util.Map;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public final class SetModelResponseToolTest {
+
+  @Test
+  public void declaration_returnsCorrectFunctionDeclaration() {
+    Schema outputSchema =
+        Schema.builder()
+            .type("OBJECT")
+            .properties(ImmutableMap.of("field1", Schema.builder().type("STRING").build()))
+            .required(ImmutableList.of("field1"))
+            .build();
+
+    SetModelResponseTool tool = new SetModelResponseTool(outputSchema);
+    FunctionDeclaration declaration = tool.declaration().get();
+
+    assertThat(declaration.name()).hasValue("set_model_response");
+    assertThat(declaration.description()).isPresent();
+    assertThat(declaration.description().get()).contains("Set your final response");
+    assertThat(declaration.parameters()).hasValue(outputSchema);
+  }
+
+  @Test
+  public void runAsync_returnsArgs() {
+    Schema outputSchema =
+        Schema.builder()
+            .type("OBJECT")
+            .properties(ImmutableMap.of("field1", Schema.builder().type("STRING").build()))
+            .build();
+
+    SetModelResponseTool tool = new SetModelResponseTool(outputSchema);
+    Map<String, Object> args = ImmutableMap.of("field1", "value1");
+
+    Map<String, Object> result = tool.runAsync(args, null).blockingGet();
+
+    assertThat(result).isEqualTo(args);
+  }
+
+  @Test
+  public void runAsync_validatesArgs() {
+    Schema outputSchema =
+        Schema.builder()
+            .type("OBJECT")
+            .properties(ImmutableMap.of("field1", Schema.builder().type("STRING").build()))
+            .required(ImmutableList.of("field1"))
+            .build();
+
+    SetModelResponseTool tool = new SetModelResponseTool(outputSchema);
+    Map<String, Object> invalidArgs = ImmutableMap.of("field2", "value2");
+
+    // Should throw validation error
+    IllegalArgumentException exception =
+        assertThrows(
+            IllegalArgumentException.class, () -> tool.runAsync(invalidArgs, null).blockingGet());
+
+    assertThat(exception).hasMessageThat().contains("does not match agent output schema");
+  }
+
+  @Test
+  public void runAsync_validatesComplexArgs() {
+    Schema complexSchema =
+        Schema.builder()
+            .type("OBJECT")
+            .properties(
+                ImmutableMap.of(
+                    "id",
+                    Schema.builder().type("INTEGER").build(),
+                    "tags",
+                    Schema.builder()
+                        .type("ARRAY")
+                        .items(Schema.builder().type("STRING").build())
+                        .build(),
+                    "metadata",
+                    Schema.builder()
+                        .type("OBJECT")
+                        .properties(ImmutableMap.of("key", Schema.builder().type("STRING").build()))
+                        .build()))
+            .required(ImmutableList.of("id", "tags", "metadata"))
+            .build();
+
+    SetModelResponseTool tool = new SetModelResponseTool(complexSchema);
+    Map<String, Object> complexArgs =
+        ImmutableMap.of(
+            "id", 123,
+            "tags", ImmutableList.of("tag1", "tag2"),
+            "metadata", ImmutableMap.of("key", "value"));
+
+    Map<String, Object> result = tool.runAsync(complexArgs, null).blockingGet();
+
+    assertThat(result).containsEntry("id", 123);
+    assertThat(result).containsEntry("tags", ImmutableList.of("tag1", "tag2"));
+    assertThat(result).containsEntry("metadata", ImmutableMap.of("key", "value"));
+  }
+}