It seems OpenAI has decided to keep the CoT results a secret. If they were to allow the model to call out to tools to help fill in the CoT steps, then this might reveal what the model is thinking - something they do not want the outside world to know about.

I could imagine OpenAI might allow their own vetted tools to be used, but perhaps it will be a while (if ever) before developers are allowed to hook up their own tools. The risks here are substantial. A model fine-tuned to run chain-of-thought that can answer graduate level physics problems at an expert level can probably figure out how to scam your grandma out of her savings too.