API doesn't return images with an explicit rating.

I’m not seeing anything in the docs about explicit images being blocked, or if I need to use my api key to access them.

I’m pretty clueless in regards to API stuff, but I believe you can make use of the filter_id parameter to work around this. I believe it uses public filters (you can create a new filter with whatever you’d like, and make it public).
 
Otherwise if you’re wanting a true ‘everything’ filter with absolutely no tags filtered, feel free to use mine which I made public already and will never alter. ID# is 3