Handoffs and multi-agent systems

One agent with ten tools and a page of instructions starts to make mistakes that two agents with five tools each do not. Lesson 09.02 gave the reason: every tool description and every instruction competes for the same attention. The fix is specialisation, and the mechanism the Agents SDK gives you for it is the handoff. A triage agent reads the message and transfers the conversation to a billing agent or a technical agent. From then on the specialist is talking to the customer, with the full history, and its own smaller set of tools.

A handoff is not a router you write. It is a tool the SDK synthesises: when you pass handoffs=[billing, technical], the triage agent's tool list gains transfer_to_billing and transfer_to_technical. The model calls one like any other tool, and the runner responds by switching the active agent rather than returning a tool result. The rest of the run happens under the new agent's instructions.