And that is exactly when you exercised your agency, and thus did not allow the players to exercise theirs.
This is a mistaken belief that not having all 3 trillion options equates to no agency. You can in fact remove 10 billion of the 3 trillion options and the players still have full agency to pick from 2 trillion 990 billion options that remain.
The players did not make the road. So what. They got a map that showed them that the road was there. So what. They still have the option to travel the road or not, pick the direction, go offroad, decide to destroy the road, pave the road, and on and on and on and on. They have full agency still.
They have the freedom to visit whatever exhibits in the museum they like. They cannot define new parameters for what constitutes an exhibit, nor can they visit something outside the museum.
Well, that's not true at all.
Player: "I go outside the museum."
or...
Player: "I go find the blah blah blah in the museum."
DM: "I didn't even think of that, but you're correct that one would be here."
Said thing wasn't described or placed into that museum until the player had his PC go to it.
Or...
Player: "Curator, you don't have a Peanut Chicpea Owlbear exhibit. They are the smallest known owlbears. There's room in the corner over there for one and I happen to have a specimen. I'll give you 1000 gold to set it up."
The player there just created a new exhibit and with that kind of money can decide all the parameters.
Again, full agency requires that the players have options for THEM to decide things that affect the game world, not every option possible.