These would be what we call "HostAccountDataElements" or "HADES".

Their presence will vary from one FI to another, also possibly vary from one product type to another. But they are available, unfortunately not on the incoming request. But a simple call will get you what you need. The data is returned in not such a great structure so just need to loop to get it into an easily accessible structure:

from q2_sdk.hq.hq_api.wedge_online_banking import GetUserAccountList

...
    account_params = GetUserAccountList.ParamsObj(self.logger, self.hq_credentials, True)
    accounts = await GetUserAccountList.execute(account_params)

    hades = {}
    for account_elem in accounts.json()['Data']['AccountListResponse']['Q2_AccountDataElements']:
        hades.setdefault(account_elem['HostAccountID'], {})[account_elem['HADEName']] = account_elem

This will leave you with a "hades" dictionary where the key is the host_account_id and the value is a dictionary where the "HADEName" is the key. (example dictionary attached).

So now for a given account you can lookup the meta-data we have for that account.

My recommendation would be to make the HADEName key's configurable so that we can set the associated HADENames you use differently per FI if for some reason they use different HADENames for Interest Rate or Origination Date.

But by default the HADENames you would be looking for are :

"IntRate" for Interest Rate.
"OrigDt" for Origination Date (yes even on non-loans)

Other HADENames can be found in Q2_HostAccountDataElement table