You need to add a section to your module's manifest denoting your action as a 'tools action.'
This section should look similar to this:
Name: com/tomwheeler/example/dataimport/wizard/DataImportCookieAction.class OpenIDE-Module-Class: Action
Don't forget to put the extra space above it, since manifest sections need to be separated this way. According to NetBeans developer Jesse Glick, this method will be deprecated sometime in the future and replaced by an entry in the layer file.
Source: NetBeans FAQ