diff --git a/libgimp/gimpbrushselectbutton.c b/libgimp/gimpbrushselectbutton.c
index 07f982b9c8..f3cce9cc44 100644
--- a/libgimp/gimpbrushselectbutton.c
+++ b/libgimp/gimpbrushselectbutton.c
@@ -243,7 +243,7 @@ gimp_brush_select_button_class_init (GimpBrushSelectButtonClass *klass)
    * @paint_mode: paint mode of the brush
    * @width: width of the brush
    * @height: height of the brush
-   * @mask_data: brush mask data
+   * @mask_data: (array) (element-type guchar): brush mask data
    * @dialog_closing: whether the dialog was closed or not.
    *
    * The ::brush-set signal is emitted when the user selects a brush.
diff --git a/libgimpbase/gimpparamspecs.c b/libgimpbase/gimpparamspecs.c
index 575762d47a..7a8e086648 100644
--- a/libgimpbase/gimpparamspecs.c
+++ b/libgimpbase/gimpparamspecs.c
@@ -29,6 +29,12 @@
  * GIMP_TYPE_ARRAY
  */
 
+/**
+ * gimp_array_new:
+ * @data: (array length=length):
+ * @length:
+ * @static_data:
+ */
 GimpArray *
 gimp_array_new (const guint8 *data,
                 gsize         length,
diff --git a/libgimpbase/gimputils.c b/libgimpbase/gimputils.c
index dd46e18610..3d213e5810 100644
--- a/libgimpbase/gimputils.c
+++ b/libgimpbase/gimputils.c
@@ -1198,7 +1198,8 @@ gimp_stack_trace_available (gboolean optimal)
  * gimp_stack_trace_print:
  * @prog_name: the program to attach to.
  * @stream: a FILE* stream.
- * @trace: location to store a newly allocated string of the trace.
+ * @trace: (out) (optional): location to store a newly allocated string of
+ *                           the trace.
  *
  * Attempts to generate a stack trace at current code position in
  * @prog_name. @prog_name is mostly a helper and can be set to NULL.
diff --git a/libgimpcolor/gimprgb.c b/libgimpcolor/gimprgb.c
index 695d5e8b20..ae97a2b348 100644
--- a/libgimpcolor/gimprgb.c
+++ b/libgimpcolor/gimprgb.c
@@ -474,7 +474,7 @@ gimp_rgba_set (GimpRGB *rgba,
  * @blue:  the blue component
  * @alpha: the alpha component
  *
- * Sets the red, green, blue and alpha components of @rgb from 8bit
+ * Sets the red, green, blue and alpha components of @rgba from 8bit
  * values (0 to 255).
  **/
 void
@@ -492,6 +492,16 @@ gimp_rgba_set_uchar (GimpRGB *rgba,
   rgba->a = (gdouble) a / 255.0;
 }
 
+/**
+ * gimp_rgba_get_uchar:
+ * @rgba:  a #GimpRGB struct
+ * @red: (out) (optional): Location for the red component
+ * @green: (out) (optional): Location for the green component
+ * @blue: (out) (optional): Location for the blue component
+ * @alpha: (out) (optional): Location for the alpha component
+ *
+ * Gets the 8bit red, green, blue and alpha components of @rgba.
+ **/
 void
 gimp_rgba_get_uchar (const GimpRGB *rgba,
                      guchar        *r,
diff --git a/libgimpconfig/gimpconfig-iface.c b/libgimpconfig/gimpconfig-iface.c
index a366a83927..4bcb9bec3f 100644
--- a/libgimpconfig/gimpconfig-iface.c
+++ b/libgimpconfig/gimpconfig-iface.c
@@ -558,7 +558,7 @@ gimp_config_deserialize_stream (GimpConfig    *config,
 /**
  * gimp_config_deserialize_string:
  * @config:   a #GObject that implements the #GimpConfigInterface.
- * @text:     string to deserialize (in UTF-8 encoding)
+ * @text: (array length=text_len): string to deserialize (in UTF-8 encoding)
  * @text_len: length of @text in bytes or -1
  * @data:     client data
  * @error:    return location for a possible error
diff --git a/libgimpwidgets/gimpintcombobox.c b/libgimpwidgets/gimpintcombobox.c
index c77daccee1..c300d751d1 100644
--- a/libgimpwidgets/gimpintcombobox.c
+++ b/libgimpwidgets/gimpintcombobox.c
@@ -529,7 +529,7 @@ gimp_int_combo_box_set_active_by_user_data (GimpIntComboBox *combo_box,
 /**
  * gimp_int_combo_box_get_active_user_data:
  * @combo_box: a #GimpIntComboBox
- * @user_data: return location for the gpointer value
+ * @user_data: (out): return location for the gpointer value
  *
  * Retrieves the user-data of the selected (active) item in the @combo_box.
  *
diff --git a/libgimpwidgets/gimppreviewarea.c b/libgimpwidgets/gimppreviewarea.c
index 3f49effaee..51436f5f02 100644
--- a/libgimpwidgets/gimppreviewarea.c
+++ b/libgimpwidgets/gimppreviewarea.c
@@ -439,7 +439,7 @@ gimp_preview_area_new (void)
  * @width:     buffer width
  * @height:    buffer height
  * @type:      the #GimpImageType of @buf
- * @buf:       a #guchar buffer that contains the preview pixel data.
+ * @buf: (array): a #guchar buffer that contains the preview pixel data.
  * @rowstride: rowstride of @buf
  *
  * Draws @buf on @area and queues a redraw on the given rectangle.
@@ -693,11 +693,11 @@ gimp_preview_area_draw (GimpPreviewArea *area,
  * @width:      buffer width
  * @height:     buffer height
  * @type:       the #GimpImageType of @buf1 and @buf2
- * @buf1:       a #guchar buffer that contains the pixel data for
- *              the lower layer
+ * @buf1: (array): a #guchar buffer that contains the pixel data for
+ *                 the lower layer
  * @rowstride1: rowstride of @buf1
- * @buf2:       a #guchar buffer that contains the pixel data for
- *              the upper layer
+ * @buf2: (array): a #guchar buffer that contains the pixel data for
+ *                 the upper layer
  * @rowstride2: rowstride of @buf2
  * @opacity:    The opacity of the first layer.
  *
@@ -1077,13 +1077,13 @@ gimp_preview_area_blend (GimpPreviewArea *area,
  * @width:          buffer width
  * @height:         buffer height
  * @type:           the #GimpImageType of @buf1 and @buf2
- * @buf1:           a #guchar buffer that contains the pixel data for
+ * @buf1: (array):  a #guchar buffer that contains the pixel data for
  *                  the lower layer
  * @rowstride1:     rowstride of @buf1
- * @buf2:           a #guchar buffer that contains the pixel data for
+ * @buf2: (array):  a #guchar buffer that contains the pixel data for
  *                  the upper layer
  * @rowstride2:     rowstride of @buf2
- * @mask:           a #guchar buffer representing the mask of the second
+ * @mask: (array):  a #guchar buffer representing the mask of the second
  *                  layer.
  * @rowstride_mask: rowstride for the mask.
  *
@@ -1832,6 +1832,14 @@ gimp_preview_area_set_color_config (GimpPreviewArea *area,
     }
 }
 
+/**
+ * gimp_preview_area_get_size:
+ * @area:   a #GimpPreviewArea widget.
+ * @width: (out): The preview areay width
+ * @height: (out): The preview areay height
+ *
+ * Gets the preview area size
+ */
 void
 gimp_preview_area_get_size (GimpPreviewArea *area,
                             gint            *width,
@@ -1964,7 +1972,7 @@ gimp_preview_area_menu_new (GimpPreviewArea *area,
 /**
  * gimp_preview_area_menu_popup:
  * @area:  a #GimpPreviewArea
- * @event: the button event that causes the menu to popup or %NULL
+ * @event: (nullable): the button event that causes the menu to popup or %NULL
  *
  * Creates a popup menu that allows one to configure the size and type of
  * the checkerboard pattern that the @area uses to visualize transparency.