feat: Support function calls in LLM event summarizer

google-genai-bot · copybara-github · commit 55144aca3c1d · 2026-01-23T10:41:54.000-08:00
The summarizer now correctly formats `FunctionCall` and `FunctionResponse` parts into the conversation history, which allows the model to be aware of tool usage when summarizing the conversation.

PiperOrigin-RevId: 860168537
diff --git a/core/src/main/java/com/google/adk/summarizer/LlmEventSummarizer.java b/core/src/main/java/com/google/adk/summarizer/LlmEventSummarizer.java
@@ -19,13 +19,17 @@
 import static java.util.function.Predicate.not;
 import static java.util.stream.Collectors.joining;
 
+import com.google.adk.JsonBaseModel;
 import com.google.adk.events.Event;
 import com.google.adk.events.EventActions;
 import com.google.adk.events.EventCompaction;
 import com.google.adk.models.BaseLlm;
 import com.google.adk.models.LlmRequest;
 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 io.reactivex.rxjava3.core.Maybe;
 import java.util.List;
@@ -108,10 +112,40 @@ private String formatEventsForPrompt(List<Event> events) {
             event ->
                 event.content().flatMap(Content::parts).stream()
                     .flatMap(List::stream)
-                    .map(Part::text)
-                    .flatMap(Optional::stream)
-                    .filter(not(String::isEmpty))
-                    .map(text -> event.author() + ": " + text))
-        .collect(joining("\\n"));
+                    .map(
+                        part ->
+                            formatPartForPrompt(
+                                event.content().flatMap(Content::role).orElse(event.author()),
+                                part))
+                    .flatMap(Optional::stream))
+        .collect(joining("\n"));
+  }
+
+  private String toJson(Object object) {
+    try {
+      return JsonBaseModel.getMapper().writeValueAsString(object);
+    } catch (Exception e) {
+      return String.valueOf(object);
+    }
+  }
+
+  private Optional<String> formatPartForPrompt(String role, Part part) {
+    return part.text()
+        .filter(not(String::isEmpty))
+        .map(t -> role + ": " + t)
+        .or(() -> part.functionCall().map(f -> formatFunctionCallToString(role, f)))
+        .or(() -> part.functionResponse().map(f -> formatFunctionResponseToString(role, f)));
+  }
+
+  private String formatFunctionCallToString(String role, FunctionCall f) {
+    return String.format(
+        "%s: [FUNCTION_CALL: %s(%s)]",
+        role, f.name().orElse("unknown"), toJson(f.args().orElse(ImmutableMap.of())));
+  }
+
+  private String formatFunctionResponseToString(String role, FunctionResponse f) {
+    return String.format(
+        "%s: [FUNCTION_RESPONSE: %s -> %s]",
+        role, f.name().orElse("unknown"), toJson(f.response().orElse(ImmutableMap.of())));
   }
 }
diff --git a/core/src/test/java/com/google/adk/summarizer/LlmEventSummarizerTest.java b/core/src/test/java/com/google/adk/summarizer/LlmEventSummarizerTest.java
@@ -28,12 +28,13 @@
 import com.google.adk.models.LlmRequest;
 import com.google.adk.models.LlmResponse;
 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 io.reactivex.rxjava3.core.Flowable;
-import java.util.HashMap;
+import java.util.Map;
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
@@ -74,7 +75,7 @@ public void setUp() {
   public void summarizeEvents_success() {
     ImmutableList<Event> events =
         ImmutableList.of(createEvent(1L, "Hello", "user"), createEvent(2L, "Hi there!", "model"));
-    String expectedConversationHistory = "user: Hello\\nmodel: Hi there!";
+    String expectedConversationHistory = "user: Hello\nmodel: Hi there!";
     String expectedPrompt =
         DEFAULT_PROMPT_TEMPLATE.replace("{conversation_history}", expectedConversationHistory);
     LlmResponse mockLlmResponse =
@@ -148,47 +149,25 @@ public void summarizeEvents_formatsEventsForPromptCorrectly() {
                 .invocationId("id2")
                 .build(),
             // Event with function call
-            Event.builder()
-                .timestamp(7L)
-                .author("model")
-                .content(
-                    Content.builder()
-                        .parts(
-                            ImmutableList.of(
-                                Part.builder()
-                                    .functionCall(
-                                        FunctionCall.builder()
-                                            .name("tool")
-                                            .args(new HashMap<>())
-                                            .build())
-                                    .build()))
-                        .build())
-                .invocationId("id3")
-                .build(),
+            createFunctionCallEvent(7L, "id3", "tool", ImmutableMap.of("key", "value")),
             // Event with function response
-            Event.builder()
-                .timestamp(8L)
-                .author("model")
-                .content(
-                    Content.builder()
-                        .parts(
-                            ImmutableList.of(
-                                Part.builder()
-                                    .functionResponse(
-                                        FunctionResponse.builder()
-                                            .name("tool")
-                                            .response(new HashMap<>())
-                                            .build())
-                                    .build()))
-                        .build())
-                .invocationId("id4")
-                .build());
+            createFunctionResponseEvent(8L, "id4", "tool", ImmutableMap.of("status", "ok")),
+            // Event with function call (add)
+            createFunctionCallEvent(9L, "id5", "add", ImmutableMap.of("a", 20, "b", 22)),
+            // Event with primitive function response
+            createFunctionResponseEvent(10L, "id6", "add", ImmutableMap.of("result", 42)));
 
     String expectedFormattedHistory =
-        "user: User says...\\n"
-            + "model: Model replies...\\n"
-            + "user: Another user input\\n"
-            + "model: More model text";
+        """
+        user: User says...
+        model: Model replies...
+        user: Another user input
+        model: More model text
+        model: [FUNCTION_CALL: tool({"key":"value"})]
+        model: [FUNCTION_RESPONSE: tool -> {"status":"ok"}]
+        model: [FUNCTION_CALL: add({"a":20,"b":22})]
+        model: [FUNCTION_RESPONSE: add -> {"result":42}]\
+        """;
     String expectedPrompt =
         DEFAULT_PROMPT_TEMPLATE.replace("{conversation_history}", expectedFormattedHistory);
 
@@ -215,4 +194,39 @@ private Event createEvent(long timestamp, String text, String author) {
         .invocationId(Event.generateEventId())
         .build();
   }
+
+  private Event createFunctionCallEvent(
+      long timestamp, String invocationId, String name, Map<String, Object> args) {
+    return Event.builder()
+        .timestamp(timestamp)
+        .author("model")
+        .content(
+            Content.builder()
+                .parts(
+                    ImmutableList.of(
+                        Part.builder()
+                            .functionCall(FunctionCall.builder().name(name).args(args).build())
+                            .build()))
+                .build())
+        .invocationId(invocationId)
+        .build();
+  }
+
+  private Event createFunctionResponseEvent(
+      long timestamp, String invocationId, String name, Map<String, Object> response) {
+    return Event.builder()
+        .timestamp(timestamp)
+        .author("model")
+        .content(
+            Content.builder()
+                .parts(
+                    ImmutableList.of(
+                        Part.builder()
+                            .functionResponse(
+                                FunctionResponse.builder().name(name).response(response).build())
+                            .build()))
+                .build())
+        .invocationId(invocationId)
+        .build();
+  }
 }
