In the Suttas we fairly commonly encounter the term uddesa is a specific sense as contrasted with vibhaṅga. The former is said to be “in brief”, the latter “in detail”. Usually uddesa is translated as “summary, synopsis”. And no doubt, it is something like that.
However, another very common sense of uddesa is “recitation”. It seems to me that these two meaning are more closely connected than is apparent if we translate using terms like “summary”.
In fact, from the usage, it seems that uddesa and vibhaṅga correspond to a very common structure of Buddhist texts. We often find a short, memorable statement,—which may be a verse, a rule, a short Dhamma saying, and so on—which was intended to be strictly memorized and recited. It would be accompanied by a longer commentary, analysis, or explanation, which would originally be more flexible, but over time would come to be fixed in the same way. I think that is exactly what uddesa means, and why it is paired with vibhaṅga. The uddesa is a short passage which is intended to be memorized literally and recited.
Consider the Bhaddekaratta Suttas. (MN 131, MN 132, MN 133, MN 134) they all contain the same uddesa, given originally by the Buddha, and specifically said to be something that one should memorize, and the vibhaṅgas which vary, and may be taught by others apart from the Buddha.
I think this is a critical feature of the early Buddhist oral texts, and we should make it clear in translation by specifying “passage for recitation” or something similar.