Use endnlib.py to perform the conversion. For example:
% endnlib.py input_refs.endn -o output_refs.endn or % endnlib.py input_refs.endn --outfile=output_refs.endn
This script sets the label field to a string containing authorYear-Firstpage. If the page field is empty, the label includes the first word in the title over 5 letters long. If the author or year fields are empty, the label will incorporate the remaining fields and append ``_badX'' (where X is the current count of bad labels) to the end. Records for which the label was successfully constructed will contain ``label_ok'' appended to the contents of the Notes field; records with bad labels will be indicated with ``label_not_ok''.
You can search for these records (which must be manually modified) in either the output_refs.endn file or the Endnote library you'll create in the next step.