I’ve been using GPT models via hax[1], a bare bones harness with minimal tools on my system and have the models rely on bash for the most part the last few months. It’s been a breath of fresh air amidst all these overengineered harnesses.
If I need special actions, I just make them CLI tools on my Mac and tell the AI model that such a tool exists(via a single line in its system prompt) and that’s it. It’s been very nice.
[1] - https://usehax.dev/
No affiliation whatsoever. Just a happy user.
You seem to care, so I wanna point out a semantic nit; "such a tool exists" could be interpreted as a harness provided tool, rather than a command line tool. (Edit, on a re-read its pretty obvious you mean cli tool, but keeping this statment here as im sure it'll open someone's eyes to the difference)
I've gotta give hax a go, as a pi user who came on-board due to the no frills direction pi takes. I say takes rather than took, because regardless of the (heated) discussion surrounding mcp and code mode support, I cannot fight the numbers- augmenting the harness provided tools is a notable boost to execution round trip performance.