If you cannot see what your recovery partner is doing, you cannot manage the outcome. The reporting standards to insist on.
Outsourcing recovery does not outsource accountability. Clients remain answerable for how their customers were treated and for the accuracy of what was collected on their behalf.
Minimum reporting should cover activity, outcomes and money: contact attempts and right-party contacts, promises made and kept, amounts recovered, and full reconciliation to remittance.
Case-level transparency matters as much as portfolio totals. You should be able to interrogate any individual account and see the complete contact history behind its current status.
Finally, insist on exception reporting: complaints, disputes and vulnerability indicators should reach you promptly rather than surfacing in a quarterly summary.