The only time it feels like cheating is if you disable the "Hidden/Unknown" tag. But by default, the mod will say "??? (Unknown)" for items you have genuinely never picked up before, preserving the discovery magic.
To use ANY mod in Repentance , you must have defeated at least once without mods enabled. Once you have that achievement, you can enable mods freely. item description mod isaac repentance
The External Item Descriptions mod was originally created by developer to solve a simple problem: The Binding of Isaac has too many items, and the game does a terrible job of explaining them. The only time it feels like cheating is
Features a built-in recipe list for Tainted Cain’s Bag of Crafting. item description mod isaac repentance