Currently our documentation for the transactions.xml endpoint states the following:

Transactions from a single batch are reported only if all of them are valid. If there is an error in processing of at least one of them, none is reported.

However, due to the nature of this request being asynchronous, the validation of this is not immediately returned.

There is a desire to have some initial validation of the request and return an immediate non 20X response if the transactions are not valid syntactically. This will allow the application sending the API request to react and not invalidate the entire list of transactions.

For example a missing app_id or user_key:

[{
  "usage": {
    "hits": 1
  }
}]

OR

[{
 "app_id": "",
  "usage": {
    "hits": 1
  }
}]

Both currently return a valid 202 response code.

In addition, this could probably also validate the timestamps as they have a 24 hour deadline and this could avoid a similar issue there.