I'm curious to know if, when creating a struct that will represent JSON data, all the properties of the struct should be optional or not?

For example: if I'm wanting to retreive data from an API and I need a struct to represent that data, is it safer to mark the properties as optional in the event that I can't get a hold of the data?

Well that depends, but if you do then you will have to unwrap them! You best of seeing the json returns maybe put them into a JSON decoder like Ducky and seeing which one are optional. However even then it might change (if you do not own the JSON). Think you will find some fields will always have values!