AWS Bedrock Agent Flaw Shows Why Validation Gates Beat Prompt Engineering

A developer building a customer support agent on AWS Bedrock discovered that the agent created bug tickets even when required fields like reproduction steps or environment details were missing, scoring only 0.83 on correctness evaluations. The root cause was the agent filling gaps with plausible assumptions rather than refusing to proceed, a behavior inherent to how large language models are trained to be helpful. The proposed fix moves validation entirely out of the model's decision-making by introducing a dedicated Lambda-based schema checker between information gathering and ticket creation. This validation gate blocks the agent from invoking ticket creation unless all required fields are confirmed present, eliminating the possibility of the model guessing its way through incomplete workflows. The case illustrates that reliable agentic systems require architectural constraints, not just better prompts, to enforce strict boundaries around incomplete or out-of-scope requests.