On the German-language Wikipedia, the Literatur template issues a warning if both OCLC and ISBN are given. In cases where both of them exist, only ISBN should be given. However, since Citoid is not aware of this, lots of articles show up in maintenance categories (local bug report).
As far as I can see in the TemplateData documentation, there is no way to specify that Citoid's oclc should only be mapped to Literatur's OCLC if Citoid's ISBN is empty. If we had a simple if-condition similar to how it is available for MediaWiki templates, we could configure the template correctly in this and many other cases.
For the case mentioned above, it would look similar to this:
"oclc": "{{#if: "ISBN" | None | "OCLC" }}", "DOI": "DOI", "ISBN": ["ISBN"],