Its not always binary. You want to throw an error at even the slight amount of error. This will annoy users, but over time as bugs and edge cases are fixed - it

Its not always binary. You want to throw an error at even the slight amount of error. This will annoy users, but over time as bugs and edge cases are fixed - it will lead to a very robust program. Meanwhile you want to save time/work for the caller. You dont want the caller to need many lines of boilerplate just to setup the call.