How does API work exactly?

I'm considering trying to make a community sheet for my favorite game line (as none exists right now). My knowledge on scripting is limited at best and even that would require a serious refresher course. The game itself has some quirky rules that would make API a necessary evil just to make the sheet functional (mostly I need exploding dice on rolling a double). My question is, can API scripts be attached to sheets on a permanent basis so everyone can use them, or do they need to be plugged in each time the sheet is used in any game? The answer to that question is the determining factor as to whether or not it is worth going to the effort of relearning what I once knew (and most likely learning a whole lot more).

Character sheets don't require any use of javascript or the api. Just HTML and CSS. They do have an option for sheetworkers which are mini-api scripts for certain tasks.

For starters, check out the  API:Introduction and  API:Use Guide sections of the Roll20 Wiki. If you have any specific questions about the API, there are tons of experts around who are always willing to help.

Character Sheets and their embedded  Sheet Workers , once in the Roll20 Repo and approved are available to anyone that wants to use them. API scripts require a  Pro level subscription for the creator of the Game in which they are used. The Dice Mechanics for your game (I remember reading some of your posts about it) would be easiest to handle in an API script.  However, you might be able to create something fairly clever in a Sheet Worker that could work as a die roller.  The biggest problem would be outputting it as I don't believe the Sheet Workers can directly write messages to chat.

Thanks for the information. Sadly, it isn't sounding too feasible.