Are there any AI tools that can validate design approaches

No. The feedback itself is too complex for an AI to validate it: you're going to have to talk to a real human if you want good feedback.

ChatGPT can be pretty good at evaluating a first pass of your system design. It can give you a good first step about how to approach a problem as well as coming up with paths to go down for your specific use case. Of course, you need to be able to think about the solution as it relates to your company's architecture.