When doing a "get transactions" in the online menu, then the value the bank transmits in the purpose-field is set as the description-field of the resulting transaction.
It would make much more sense, if it instead would be written into the memo-field of the corresponding split (since on another bank account, the same transaction gets another purpose field).
At least it would be nice, if the user had the choice in which of the fields he wants the entry to be written.
Personally I prefer a simple and clear text in the description field, while the value from my bank is usually kind of cryptical.