Passing work from one agent to another cleanly. The receiving agent needs enough context to continue and not so much that it inherits the confusion. Most multi-agent failures happen at these boundaries, where something the first agent knew implicitly never made it into the message.
Technical view
Requires an explicit contract specifying what is transferred: task statement, relevant artefacts, constraints, and what has already been tried and failed. Passing full conversation history is simple and pollutes context; passing a summary is cleaner and loses detail. Structured handoff objects with defined fields are more reliable than free text. Failures should be attributable to a handoff, which requires logging the exact content transferred.
Related
Part of AI Terminology Index, section: Agents and Tools.