Name Description
Browseable This Boolean property controls whether your property is shown by default in the ToolPane under the custom properties category. Set this property to false if you want to create your own custom ToolPart to display your property or if you do not want users to change your custom property through the built-in UI. Also, if you set WebPartStorage to Storage.None, your custom property is not shown.
Category The title section of the category you want your property placed into. If you do not specify one, your property is put into the Custom Properties category.
DefaultValue The default value for your property if there one.
Description The contents of the tooltip if the user hovers over your property in the Toolpane.
Editor This attribute allows you to specify the property builder to launch.
FriendlyName The caption displayed for the custom property in the ToolPane. If you do not specify this, the property name is used.
HtmlDesigner This attribute specifies whether the property has an HTML builder associated with it and determines which HTML property builder to launch.
ReadOnly Set this boolean property to true if you want your custom property to be read-only. You can also not supply a set accessor which will make your property read-only.
WebPartStorage This property allows you to set the customization of your Web Parts. Set to Storage.Shared to make changes to the property global. Set to Storage.Personal to allow per user customization of the property. Set to Storage.None if you don't want the setting to persist for the custom property. Also, as part of this property, you can pass ControlledExport = True. This will stop your property from being exported via the export functionality.

Table 1. Possible Attributes for Custom Web Part Properties