Daggerheart builds in a degree of player-contribution as a core expectation. It's in the Player's Agenda/Principles, and the GM stuff as well. As @nyvinter said, the most "immersion" promoting way to do this is to ask the character how something relates to their background or knowledge. As an example, when the Sorcerer in my game used their innate detect magic ability I turned to them and went "yeah, you can detect a lingering old enchantment on these walls - but there's something deeper. How can you tell there's a thread of Magelord magic coming from somewhere within?"
They're not necessarily asserting facts about the world that "cross the line," they're defining what it feels like to their character for this thing to be true. It does help to give them something to crystalize off of (and I know some of my players are helped by a bit of a "pick list" to give them a springboard).
I haven't personally had a player dislike it. I'm super freaking up front about how the game expects this to be a core bit of play, and literally every player I have volunteering to try the game has highlighted it as a core draw.
They're not necessarily asserting facts about the world that "cross the line," they're defining what it feels like to their character for this thing to be true. It does help to give them something to crystalize off of (and I know some of my players are helped by a bit of a "pick list" to give them a springboard).
I haven't personally had a player dislike it. I'm super freaking up front about how the game expects this to be a core bit of play, and literally every player I have volunteering to try the game has highlighted it as a core draw.
) but I have used the player description technique in other games. I try to offer it up only to players that I know appreciate it, and if they have nothing, that’s fine too. 
