diff --git a/TODO b/TODO
index cc53f1b9..1c402bba 100644
--- a/TODO
+++ b/TODO
@@ -1,3 +1,31 @@
+- vips_object_set_property() for output args should expect a pointer to the
+  location to write the value to on _build()
+
+  nope, won't work
+
+  try 2) init all output VipsImage to a "p" image and output args are never
+  required ... instead, after _build(), you can read them out with get_prop
+  and copy them whereever you like
+
+  	int im_add( in1, in2, out )
+	{
+		VipsImage *x;
+		VipsOperation *op;
+
+		if( !(op = vips_call( "add", in1, in2 )) )
+			return( -1 );
+		x = g_object_get_property( op, "out" );
+		if( im_copy( x, out ) ) {
+			g_object_unref( op );
+			return( -1 );
+		}
+		g_object_unref( op );
+
+		return( 0 );
+	}
+
+
+
 
 - vips_object_set_argument_from_string() leaks output images, because it has
   to, does this matter?
@@ -9,10 +37,19 @@
 
   	vips_call( "add", in1, in2, &out )
 
-  writes output to &out
+  writes output to a "p" image on &out
 
   how would this work for the CLI wrapper
 
+  vips7 compat adds another copy:
+
+  	int im_add( in1, in2, out )
+	{
+		VipsImage *x;
+
+		return( vips_call( "add", in1, in2, &x ) ||
+			im_copy( x, out ) );
+	}
 
 
 
diff --git a/libvips/iofuncs/operation.c b/libvips/iofuncs/operation.c
index da9e9c45..52e28d5b 100644
--- a/libvips/iofuncs/operation.c
+++ b/libvips/iofuncs/operation.c
@@ -481,8 +481,11 @@ vips_call_options_add( VipsObject *object,
 		entry[0].arg = G_OPTION_ARG_CALLBACK;
 		entry[0].arg_data = (gpointer) vips_call_options_set;
 		entry[0].description = g_param_spec_get_blurb( pspec );
-		entry[0].arg_description = 
-			g_type_name( G_PARAM_SPEC_VALUE_TYPE( pspec ) );
+		if( G_IS_PARAM_SPEC_BOOLEAN( pspec ) ) 
+			entry[0].arg_description = NULL;
+		else
+			entry[0].arg_description = 
+				g_type_name( G_PARAM_SPEC_VALUE_TYPE( pspec ) );
 
 		entry[1].long_name = NULL;