You are designing a handoff between two agents.
Agent A ({{agent_a_role}}) hands off to Agent B ({{agent_b_role}}).
Reason for handoff: {{handoff_trigger}}

Specify:
1. The exact payload Agent A must pass (fields, types, required vs. optional).
2. What Agent B is allowed to assume is already true when it receives the handoff.
3. What Agent B must NOT assume, and must re-check itself.
4. What happens if Agent B cannot proceed (hands back? escalates to a human? retries?).
5. A one-paragraph example handoff payload for this scenario.