To direct DITA2Go to generate only contents, or both contents and index, for Eclipse Help:
[EclipseHelpOptions] ; ListType (for filter to create) = Contents (default) ; or Both (with index, for Eclipse 3.2+) ListType = Contents
When ListType=Contents (the default), DITA2Go creates only toc.xml.
When ListType=Both, DITA2Go creates both toc.xml and index.xml.
Contents file toc.xml is required for Eclipse Help. Index file index.xml is supported only in Eclipse version 3.2 and later versions.
You can choose how DITA2Go generates data files needed for Eclipse Help contents and index; however, most likely you will never have a reason to change the default setting:
[EclipseHelpOptions] ; RefFileType = Full (default) or Body. RefFileType = Full
RefFileType values have the following effects:
Only Eclipse version 3.2 and later versions support index.xml.
§16.3.1 Modifying contents or index production for HTML-based Help.