Wikipedia's Citoid extension expects a citation in the mediawiki (not mediawikibasefields) format.

However, Web2Cit-Core's uses mediawikibasefields format.

To prevent making two requests to the Citoid service, we will probably have to make a mediawiki request instead, and address T306132.

The goal of having this citoid option was to enable the user script (i.e., integration with Wikipedia) to show both Citoid and Web2Cit results without having to make two separate requests to the Citoid API.

However, as introduced in my previous comment, Citoid results depend on a mediawiki-format Citoid response, wheras Web2Cit results depend on a mediawiki-basefields Citoid response.

It has been discussed previously whether it makes sense that Citoid results depend on a mediawiki-format Citoid response, but this will probably continue to be the case.

As suggested in my previous comment, to deal with this we could (1) have the Web2Cit-Core request mediawiki citations from the Citoid API (instead of mediawiki-basefields), and (2) address T306132 to internally convert from mediawiki to mediawiki-basefields. Remember we want to use mediawiki-basefields in Web2Cit because otherwise Citoid selection steps may have to be revised if the item type returned by Citoid changes.

However, to do so we would require a map between Zotero fields and basefields. In the event that Zotero updates this map, it would be updated in the Citoid API, and if we don't update too, our mediawiki-basefields citation may diverge from that returned by the Citoid API, which users may use to decide how to configure their Citoid selection steps.

For this reason, I think we should move forward without implementing this citoid option, which means we will have to make two separate Citoid requests to show Citoid and Web2Cit results in the custom user script.

We may revise this decision when we have implemented our Web2Cit-Editor, given that at that moment users won't rely on Citoid's mediawiki-basefields response to decide how to configure their Citoid selection steps, but rather on our internal conversion from mediawiki to mediawiki-basefields.

Nonetheless, and having said all of that, we may still consider implementing this citoid option, given how unlikely it may be that the "field to basefield" map changes so often.