Are there guidelines for how to narrate different degrees of success/failure?

I find myself getting caught up in a story and sometimes when players roll skill checks I give them the information or allow for a success depending on several factors(their description, their character, my mood, whether it adds to the story or adds flair), I’d like to be able to start keeping skill check descriptions more consistent.

For example:

Let’s say I have a player at the table that loves to blackflip, and depending on the situation that DC changes, for instance difficult terrain might make it harder where just walking through the streets of a well laid out city it would be easier.

For all intents and purposes let’s say there’s no additional DC and a backflip is a 10, so the character rolls and gets a 9.

I say “Well you feel like you have it and just at the last moment your foot lands sideways and you fall.”

Or I have players investigating a room, there’s a secret door that has a DC 15 investigation check on it. My player rolls a 14, I say “You take note that someone was recently in the room, and some papers are shuffled on the desk.”

Should I simply set my DC for things and then pass/fail? Is there anything I might be able to reference for this?