diff --git a/libs/binder/ndk/include_platform/android/binder_manager.h b/libs/binder/ndk/include_platform/android/binder_manager.h
index 5df0012..0668472 100644
--- a/libs/binder/ndk/include_platform/android/binder_manager.h
+++ b/libs/binder/ndk/include_platform/android/binder_manager.h
@@ -26,6 +26,9 @@
  * This registers the service with the default service manager under this instance name. This does
  * not take ownership of binder.
  *
+ * WARNING: when using this API across an APEX boundary, it should only be used with stable
+ * AIDL services. TODO(b/139325195)
+ *
  * \param binder object to register globally with the service manager.
  * \param instance identifier of the service. This will be used to lookup the service.
  *
@@ -39,6 +42,9 @@
  * service is not available This also implicitly calls AIBinder_incStrong (so the caller of this
  * function is responsible for calling AIBinder_decStrong).
  *
+ * WARNING: when using this API across an APEX boundary, it should only be used with stable
+ * AIDL services. TODO(b/139325195)
+ *
  * \param instance identifier of the service used to lookup the service.
  */
 __attribute__((warn_unused_result)) AIBinder* AServiceManager_checkService(const char* instance);
@@ -48,6 +54,9 @@
  * it. This also implicitly calls AIBinder_incStrong (so the caller of this function is responsible
  * for calling AIBinder_decStrong).
  *
+ * WARNING: when using this API across an APEX boundary, it should only be used with stable
+ * AIDL services. TODO(b/139325195)
+ *
  * \param instance identifier of the service used to lookup the service.
  */
 __attribute__((warn_unused_result)) AIBinder* AServiceManager_getService(const char* instance);
@@ -78,6 +87,9 @@
  * This also implicitly calls AIBinder_incStrong (so the caller of this function is responsible
  * for calling AIBinder_decStrong).
  *
+ * WARNING: when using this API across an APEX boundary, it should only be used with stable
+ * AIDL services. TODO(b/139325195)
+ *
  * \param instance identifier of the service used to lookup the service.
  *
  * \return service if registered, null if not.