We currently support a limited basic set of citation fields. See https://meta.wikimedia.org/wiki/Web2Cit/Docs/Fields

For each of these fields we had to define:

• to what Citoid/Zotero field they should be mapped (thus defining some sort of field groups),
• validation rule,
• label, and
• comparison function (for scoring against expected output).

The community has often expressed interest in supporting more of Citoid/Zotero fields. See for example here, here and T321669.

Consider supporting all Citoid/Zotero fields. Maybe some basic validation and scoring function may be considered at first. Also consider whether some fields require special treatment, as is the case with author fields.

Maybe consider beginning with fields used in Wikipedia Citation templates only, as defined in citation template's maps.citoid object.