Hi thanks for all the SDK documentation in general it's been very easy getting going a day after I got my playdate 
One idea though, if you were to add EmmyLua style documentation to the lua files in CoreLibs, people who are using sumneko_lsp (neovim users for sure, and I think microsoft vscode too?) would get a lot of help.
For example now in neovim I can get this, which is pretty good
please look a the top part of the image later on
but with a few comments on that method in __stub.lua
---Draws the filled rectangle r or the rect at (x, y) of the given width and height.
---@param x integer|rect #starting x position or rect
---@param y integer #starting y position
---@param width integer #width of rectangle
---@param height integer #height of rectangle
function playdate.graphics.fillRect(x, y, width, height) end
it has a lot more help
please look at the bottom part of the following image
(sorry for having a screenshot of screenshots but after pressing create thread I found out that uesrs on this site can't post two screenshots in a single post)
Then also you can make sure that callback functions have the right paramters, you're not passing table in when it should be a string, even any functions that take tables, that those tables have the proper items. Just a ton of nice quality of life things the LSP can do if it has more information.