fix: widen Integer to Long in castValue() for boxed Long parameter

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

@@ -450,9 +450,12 @@ private Object castValue(Object value, Class<?> type) {
       }
     }
     if (type.equals(Long.class) || type.equals(long.class)) {
-      if (value instanceof Long || value instanceof Integer) {
+      if (value instanceof Long) {
         return value;
       }
+      if (value instanceof Integer i) {
+        return i.longValue();
+      }
     } else if (type.equals(Double.class) || type.equals(double.class)) {
       if (value instanceof Double d) {
         return d.doubleValue();

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

@@ -299,6 +299,31 @@ public void call_withAllSupportedParameterTypes() throws Exception {
                 .buildOrThrow());
   }
 
+  @Test
+  public void call_withPrimitiveLongParam_whenModelProvidesInteger_succeeds() throws Exception {
+    // When the model returns a small integer (e.g. 42), Jackson deserializes it as Integer.
+    // Primitive long was never broken — Java reflection auto-widens int to long.
+    FunctionTool tool = FunctionTool.create(Functions.class, "echoPrimitiveLong");
+
+    Map<String, Object> result =
+        tool.runAsync(ImmutableMap.of("value", Integer.valueOf(42)), toolContext).blockingGet();
+
+    assertThat(result).containsExactly("value", 42L);
+  }
+
+  @Test
+  public void call_withBoxedLongParam_whenModelProvidesInteger_succeeds() throws Exception {
+    // When the model returns a small integer (e.g. 42), Jackson deserializes it as Integer.
+    // Boxed Long was broken before the fix — castValue() returned the raw Integer, causing
+    // reflection to throw IllegalArgumentException (Integer is not assignable to Long).
+    FunctionTool tool = FunctionTool.create(Functions.class, "echoBoxedLong");
+
+    Map<String, Object> result =
+        tool.runAsync(ImmutableMap.of("value", Integer.valueOf(42)), toolContext).blockingGet();
+
+    assertThat(result).containsExactly("value", 42L);
+  }
+
   @Test
   public void create_withPojoParamWithFields() {
     FunctionTool tool = FunctionTool.create(Functions.class, "pojoParamWithFields");
@@ -1064,6 +1089,14 @@ public static ImmutableMap<String, Object> returnAllSupportedParametersAsMap(
           .buildOrThrow();
     }
 
+    public static ImmutableMap<String, Object> echoPrimitiveLong(long value) {
+      return ImmutableMap.of("value", value);
+    }
+
+    public static ImmutableMap<String, Object> echoBoxedLong(Long value) {
+      return ImmutableMap.of("value", value);
+    }
+
     public static ImmutableMap<String, Object> returnsParameterizedList(
         List<Map<String, String>> listParam, ToolContext toolContext) {
       return ImmutableMap.<String, Object>builder().put("listParam", listParam).buildOrThrow();