In the interests of fairness, they do support, and do not charge for, "bangs" that defer the search to that site. They even support creating your own custom one

In the interests of fairness, they do support, and do not charge for, "bangs" that defer the search to that site. They even support creating your own custom ones which is really nice. Wikipedia is one of the default ones. According to their docs you can search it with "w! query", "!w query", "query w!", "query !w" or even add the bang to a "quick" list and use something like "w query". Unfortunately, you do give up consistency and whatever filtering/ranking/customisation Kagi offer.