Yep, text to speech (self voicing and clipboard voicing) and keyboard/controller support are built into the engine we used for the game, Ren'Py. We have toggle-able image descriptions, which are treated like any other text that would be read by the voice to text functions, for in-game visuals that aren't described in the main story.
Excellent! It seems as though you've gone above and beyond most other devs in making your game truly accessible. That's hugely appreciated!
Just a couple of clarifications if you've got the time... :)
Are visual indicators on controls, such as status' represented in text? Also, can the entire UI be navigated with the keyboard alone?
I'm sorry for how long it has taken for me to get back to you.
What I mean by visual indicators is, for instance, the toggled status of a button, the health of a player on their character icon, the unavailability of an option ETC.
Another thing to look out for which I neglected to mention before is exclusively visual puzzles. I.E a puzzle that you couldn't do blindfolded. Asking the player to look at something, move colored tiles, pick a picture out, remember the detail of a painting that wasn't described in text ETC.
Just things to check for. :)