> ANTHROPIC_MODEL=claude-3-haiku-20240307 > Why?

Probably because of cost and speed. Imagine asking a tool to get a list of your Amazon orders. This experiment shows it might code a solution and execute it and come back to you in 60 seconds. You cannot rely on the results because LLMs are non-deterministic. If you use a thinking model like GPT-5, the same might take 10 minutes to execute and you still cannot rely on the results.