feat: Fix a handful of small changes related to headers, logging and javadoc

core/src/main/java/com/google/adk/events/EventStream.java

@@ -20,7 +20,12 @@
 import java.util.NoSuchElementException;
 import java.util.function.Supplier;
 
-/** Iterable stream of {@link Event} objects. */
+/**
+ * Iterable stream of {@link Event} objects.
+ *
+ * <p>NOTE: This class is not thread-safe. Concurrent iteration from multiple threads should be
+ * avoided or externally synchronized.
+ */
 public class EventStream implements Iterable<Event> {
 
   private final Supplier<Event> eventSupplier;

core/src/main/java/com/google/adk/events/ToolConfirmation.java

@@ -62,7 +62,7 @@ public abstract static class Builder {
 
     /** For internal usage. Please use `ToolConfirmation.builder()` for instantiation. */
     @JsonCreator
-    private static Builder create() {
+    static Builder create() {
       return new AutoValue_ToolConfirmation.Builder();
     }
 

core/src/main/java/com/google/adk/examples/ExampleUtils.java

@@ -20,17 +20,22 @@
 
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.adk.JsonBaseModel;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.genai.types.Content;
 import com.google.genai.types.FunctionCall;
 import com.google.genai.types.FunctionResponse;
 import com.google.genai.types.Part;
 import java.util.List;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /** Utility class for examples. */
 public final class ExampleUtils {
 
+  private static final Logger logger = LoggerFactory.getLogger(ExampleUtils.class);
+
   // Constant parts of the example string
   private static final String EXAMPLES_INTRO =
       "<EXAMPLES>\nBegin few-shot\nThe following are examples of user queries and"
@@ -50,7 +55,7 @@ public final class ExampleUtils {
   private static final String FUNCTION_RESPONSE_PREFIX = "```tool_outputs\n";
   private static final String FUNCTION_RESPONSE_SUFFIX = "\n```\n";
 
-  private static final ObjectMapper objectMapper = new ObjectMapper();
+  private static final ObjectMapper objectMapper = JsonBaseModel.getMapper();
 
   /**
    * Converts a list of examples into a formatted few-shot prompt string.
@@ -143,6 +148,7 @@ private static void appendFunctionResponse(FunctionResponse response, StringBuil
           .append(objectMapper.writeValueAsString(responseMap))
           .append(FUNCTION_RESPONSE_SUFFIX);
     } catch (JsonProcessingException e) {
+      logger.error("Failed to serialize function response", e);
       builder.append(FUNCTION_RESPONSE_PREFIX).append(FUNCTION_RESPONSE_SUFFIX);
     }
   }

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

@@ -1,3 +1,19 @@
+/*
+ * Copyright 2026 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 com.google.adk.agents.ReadonlyContext;

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

@@ -31,6 +31,7 @@
  * execution.
  */
 public final class BuiltInCodeExecutionTool extends BaseTool {
+  public static final BuiltInCodeExecutionTool INSTANCE = new BuiltInCodeExecutionTool();
 
   public BuiltInCodeExecutionTool() {
     super("code_execution", "code_execution");

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

@@ -1,3 +1,19 @@
+/*
+ * 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 com.google.adk.models.LlmRequest;

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

@@ -24,6 +24,8 @@
 import com.google.genai.types.Tool;
 import io.reactivex.rxjava3.core.Completable;
 import java.util.List;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * A built-in tool that is automatically invoked by Gemini 2 models to retrieve search results from
@@ -41,6 +43,7 @@
  * }</pre>
  */
 public final class GoogleSearchTool extends BaseTool {
+  private static final Logger logger = LoggerFactory.getLogger(GoogleSearchTool.class);
   public static final GoogleSearchTool INSTANCE = new GoogleSearchTool();
 
   public GoogleSearchTool() {
@@ -65,7 +68,7 @@ public Completable processLlmRequest(
     String model = llmRequestBuilder.build().model().get();
     if (model != null && model.startsWith("gemini-1")) {
       if (!updatedToolsBuilder.build().isEmpty()) {
-        System.out.println(configBuilder.build().tools().get());
+        logger.error("Tools already present: {}", configBuilder.build().tools().get());
         return Completable.error(
             new IllegalArgumentException(
                 "Google search tool cannot be used with other tools in Gemini 1.x."));

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

@@ -1,3 +1,19 @@
+/*
+ * 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 com.google.adk.models.LlmRequest;

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

@@ -1,3 +1,19 @@
+/*
+ * 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 com.google.adk.agents.ReadonlyContext;

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

@@ -1,3 +1,19 @@
+/*
+ * 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 com.google.adk.agents.ReadonlyContext;

core/src/main/java/com/google/adk/tools/applicationintegrationtoolset/IntegrationConnectorTool.java

@@ -1,3 +1,19 @@
+/*
+ * 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.applicationintegrationtoolset;
 
 import static com.google.common.base.Strings.isNullOrEmpty;
@@ -26,10 +42,14 @@
 import java.util.Map;
 import java.util.Optional;
 import org.jspecify.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /** Application Integration Tool */
 public class IntegrationConnectorTool extends BaseTool {
 
+  private static final Logger logger = LoggerFactory.getLogger(IntegrationConnectorTool.class);
+
   private final String openApiSpec;
   private final String pathUrl;
   private final String connectionName;
@@ -129,7 +149,7 @@ public Optional<FunctionDeclaration> declaration() {
               .build();
       return Optional.of(declaration);
     } catch (Exception e) {
-      System.err.println("Failed to get OpenAPI spec: " + e.getMessage());
+      logger.error("Failed to get OpenAPI spec", e);
       return Optional.empty();
     }
   }
@@ -156,7 +176,7 @@ public Single<Map<String, Object>> runAsync(Map<String, Object> args, ToolContex
             String response = executeIntegration(args);
             return ImmutableMap.of("result", response);
           } catch (Exception e) {
-            System.err.println("Failed to execute integration: " + e.getMessage());
+            logger.error("Failed to execute integration", e);
             return ImmutableMap.of("error", e.getMessage());
           }
         });

core/src/main/java/com/google/adk/utils/ModelNameUtils.java

@@ -1,9 +1,25 @@
+/*
+ * 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.utils;
 
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
-public class ModelNameUtils {
+public final class ModelNameUtils {
   private static final Pattern GEMINI_2_PATTERN = Pattern.compile("^gemini-2\\..*");
   private static final Pattern PATH_PATTERN =
       Pattern.compile("^projects/[^/]+/locations/[^/]+/publishers/[^/]+/models/(.+)$");