fix: non-map value returned by a Function Tool should be automatically wrapped into a Map as per https://google.github.io/adk-docs/tools-custom/function-tools/#return-type

Mateusz Krawiec · copybara-github · commit 88a8b19fa67d · 2025-12-02T07:13:16.000-08:00
PiperOrigin-RevId: 838719814
diff --git a/core/src/main/java/com/google/adk/tools/FunctionTool.java b/core/src/main/java/com/google/adk/tools/FunctionTool.java
@@ -237,9 +237,12 @@ private Maybe<Map<String, Object>> call(Map<String, Object> args, ToolContext to
           .map(
               data -> OBJECT_MAPPER.convertValue(data, new TypeReference<Map<String, Object>>() {}))
           .toMaybe();
-    } else {
+    } else if (result instanceof Map) {
       return Maybe.just(
           OBJECT_MAPPER.convertValue(result, new TypeReference<Map<String, Object>>() {}));
+    } else {
+      // See https://google.github.io/adk-docs/tools-custom/function-tools/#return-type
+      return Maybe.just(ImmutableMap.of("result", result));
     }
   }
 

Original file line number	Diff line number	Diff line change
`@@ -237,9 +237,12 @@ private Maybe<Map<String, Object>> call(Map<String, Object> args, ToolContext to`
`237`	`237`	`.map(`
`238`	`238`	`data -> OBJECT_MAPPER.convertValue(data, new TypeReference<Map<String, Object>>() {}))`
`239`	`239`	`.toMaybe();`
`240`		`- } else {`
	`240`	`+ } else if (result instanceof Map) {`
`241`	`241`	`return Maybe.just(`
`242`	`242`	`OBJECT_MAPPER.convertValue(result, new TypeReference<Map<String, Object>>() {}));`
	`243`	`+ } else {`
	`244`	`+ // See https://google.github.io/adk-docs/tools-custom/function-tools/#return-type`
	`245`	`+ return Maybe.just(ImmutableMap.of("result", result));`
`243`	`246`	`}`
`244`	`247`	`}`
`245`	`248`