Structured Task Schema Cut AI Agent Handoff Failures from 31% to 7%

A developer building a fully autonomous coding system discovered that natural-language task handoffs between a planner agent and implementer sub-agents caused roughly one in three runs to solve the wrong problem. The root issue was that implementer agents started with zero shared context, so ambiguous instructions led to misidentified files and unintended scope creep. After a specific incident where an implementer fixed the wrong export job for three days undetected, the developer replaced free-text handoffs with a strict structured schema the planner must emit and the implementer must echo back before writing any code. This contract-style interface reduced failed or misdirected task runs from 31% to 7%. As a bonus, the same schema was reused as input for a separate verifier agent, improving end-to-end review consistency.