What is the BEST description of an operational level agreement (OLA)?

In ITIL, an Operational Level Agreement is defined as an agreement between an IT service provider and another internal part of the same organization, such as a network team or facilities group. It underpins the SLA by specifying the mutual responsibilities and commitments of internal teams, ensuring the service provider can meet its external service level commitments.

An agreement between the service provider and an external organization describes an Underpinning Contract, not an OLA.

A document describing how services will be operated day-to-day for a customer aligns more closely with a service level agreement or service description, not an OLA.

A document describing business services to operational staff describes content more akin to a service catalogue entry or operational procedure, not an OLA.