@DavyGreenwind following up on this, does the skill section (or perhaps exploration or social encounters) call out that the DM may ask for a check based on what the player describes their character as doing, even if they didn't take one of the explicit actions called out? Or conversely, does the Actions section mention anything about DMs calling for ability checks based on other things that the PC might do?
What I'm trying to get at is, does the PHB make it clear that if you as a player say "I want to sneak past the guards" that the DM may ask for a Dexterity (Stealth) check and will have set a DC for how difficult that is to acomplish.