mccPeople who design APIs. I am begging you. It doesn't matter how "simple" or "intuitive" or "elegant" your API is. You need to include sample code.
Another thing I am begging of people who make APIs: When you include sample code in the docs, include the "using"/"use"/"import"/"#include" statements. Please. Please. I just pasted this inline sample code https://mlem.ellpeck.de/articles/ui.html#setting-it-up into my hello world program, and it's failing because the symbol "UntexturedStyle" could not be found. "Are you missing a using directive or an assembly reference?", asks dotnet. Yeah, probably?? because you didn't tell me what using directives I needed?!?
"But it's obvious" I'M READING THE "GETTING STARTED" DOCUMENTATION. OBVIOUSLY I HAVE NO BASIS FOR COMPREHENDING WHAT IS OR ISN'T OBVIOUS
One other recurring thing that makes me tear my hair out in documentation: You document the type of the argument/variable/return value, but you don't document the *units*. Okay, so it's a rotation. But is it in degrees? Radians? [0.0, 1.0)? Is this time parameter in seconds, milliseconds, nanoseconds, CPU ticks? What direction is "Z"?! What is the handedness of your coordinate system?!!
Josué Boisvert 
@mcc I don't remember where, but the most cursed thing I had to work with was half revolution unit, meaning a full rotation was 2.0, at least you just have to multiply by PI to get the radian but for a solid week I kept pulling my hair as to why my rotations where fucked up. Nowhere I looked mentioned it wasn't radians.