First the loose thinking and the building up of a structure on unsound foundations and then the correction to stricter thinking and the substitutions a new underpinning beneath the already constructed mass.
Gregory Bateson on the advance of science. (From Steps to an Ecology of Mind)
This expresses a process I have observed in developers. We can develop something faster than we can define it.
That loose thinking includes the construction of loose code. We think with our fingers and eyes, keyboards and screens, editors and runtimes as well as with our brains. We try things, we draw them out or code them up. This eliminates a lot of impossible paths.
Then afterward, we shore up the useful ones. We put an API around it, error handling within, types throughout. We describe its interface and action in documentation.
Bateson grants permission to code loosely as an extension to thinking loosely, with the responsibility to return with rigor before we rope in other teams.
So do this, play in code the way we play in thought.
Then please realize that putting the foundations under it, defining the functionality so others can use it, is 10-100 times more time-consuming than your happy-path sketch.