You can distinguish tools from actions by the names of menu items. Tools have Tool in the menu entry title. Actions do not. For example, the Curve Editing Tool is a tool, but the Attach Curves menu item is an action.
If you change an action to a tool, Maya adds Tool to its name in the main menu and option window. If you change the tool back to an action, Tool is removed from the name. Regardless of whether a feature is a tool or action, the order in which you select objects or components stays the same.
Option windows for tools and actions include an Edit option menu at the top of the window that allows you to pick between tool and action modes. Currently, only actions can be switched to tool mode. Therefore, for tools (for example, Birail Surface Tool), the Edit option menu is disabled.
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