The old stdlib has a nice API reference in it’s README on Github:
The new stdlib doesn’t have an API reference on Github or on Observable (as far as I can tell):
It appears to be the case that most of the “old” and “new” stdlib are the same, but I’m not sure. So, I don’t feel confident relying on the old API reference, but I don’t know of an alternative.
If the new API could be documented by copying the old README and making a relatively small number of edits, that might be worth doing sooner rather than later.