When you build an AI system for marketing performance monitoring, one tempting idea is to let the LLM decide everything. Campaign pacing is off. Creative frequency is too high. A product category is spending inefficiently. So the natural thought is: Let’s send the current issue and previous issue to the LLM and ask if this is new, recurring, worsening, or improving. Something like this: state = llm . invoke ( f """ Last week this advertiser had issue: { issue . description } Previous metric: { i