The POST / create limits are documented on the support pages I linked above.
“For instance, a user can post 2400 tweets per day, broken down into hourly intervals.” - so you can essentially code this knowledge into an app.
However, even if you were to code to a notional limit of 100 tweets per hour, for example, you might still be rate-limited if the system detected abnormal behaviour (via adaptive rules enforced by something like botmaker).
This is one of the reasons why there are no endpoints that expose the rate limits for object creation / modification. It is much easier to rate-limit the read operations on the system.
We definitely want to clean up the documentation around this whole area so that developers have a better view into these limits in a single place; but at the moment there are no plans to add an API feature to expose the POST limits. Thanks for the feedback on this, though - we do take these kinds of discussion into consideration as we plan ahead.