I constantly come back to some of the incredibly high quality documentation I see in places like Plaid, as my examples. Provide API docs, with examples, bonus if you can provide multi-language samples. Doing so saves me tremendous amounts of time in both evaluation, and implementation. It directly leads to my recommending services to others.

Every single time I have to decode what the API docs are supposed to mean, and then deal with the reality become a war story on why not to integrate with "X".

I wish "real" documentation and auto-generated method or endpoint documentation were more clearly different things. The "how do to more than hello world" examples are absolutely the key to getting started with something new.