How do you tell your kids that you are too tired from work and you won't be able to play or attend to them as you need to rest first?

As much as possible I still spend time with the kids even if I'm dead tired from work as I don't want them to feel neglected in any way. The only time I ask for a little time alone to sleep is when I am sick. I tell them to play with their dad as mama needs to rest so we can play again later when mama wakes up.