diff --git a/engine/include/gf_type/client.h b/engine/include/gf_type/client.h
index dcc9ac1..43beceb 100644
--- a/engine/include/gf_type/client.h
+++ b/engine/include/gf_type/client.h
@@ -19,6 +19,17 @@
 
 /* Standard */
 
+/**
+ * @struct gf_client_t
+ * @~english
+ * @brief Client interface
+ *
+ * @var gf_client_t::engine
+ * @brief Engine instance
+ *
+ * @var gf_client_t::draw
+ * @brief Drawing interface
+ */
 GF_DECLARE_TYPE(client, {
 	gf_engine_t* engine;
 	gf_draw_t*   draw;
diff --git a/engine/include/gf_type/gui.h b/engine/include/gf_type/gui.h
index 417cddb..9fa7ebe 100644
--- a/engine/include/gf_type/gui.h
+++ b/engine/include/gf_type/gui.h
@@ -106,6 +106,9 @@ GF_DECLARE_TYPE(gui_component, {
  * @~english
  * @brief GUI
  *
+ * @var gf_gui_t::engine
+ * @brief Engine instance
+ *
  * @var gf_gui_t::draw
  * @brief Drawing interface
  *
diff --git a/engine/include/gf_type/server.h b/engine/include/gf_type/server.h
index 24bc010..96bcbe8 100644
--- a/engine/include/gf_type/server.h
+++ b/engine/include/gf_type/server.h
@@ -19,6 +19,17 @@
 
 /* Standard */
 
+/**
+ * @struct gf_server_t
+ * @~english
+ * @brief Server interface
+ *
+ * @var gf_server_t::engine
+ * @brief Engine instance
+ *
+ * @var gf_server_t::physics
+ * @brief Physics interface
+ */
 GF_DECLARE_TYPE(server, {
 	gf_engine_t*  engine;
 	gf_physics_t* physics;