So you think there should be a completely different AI model (or maybe the same model) with its own system prompt, that gets the requests, analyzes it, and chooses a system prompt to use to respond to it, and then runs the main model (which may be the same model) with the chosen prompt to respond to it, adding at least one round trip to every request?
You'd have to have a very effective prompt selection or generation prompt to make that worthwhile.
I'd probably reach for like embeddings though to find a relevant prompt info to include
So, tool selection, instead of being dependent on the ability of the model given the information in context, is dependent on both the accuracy of a RAG-like context stuffing first and then the model doing the right thing given the context.
I can't imagine that the number of input prompt tokens you save doing that is going to ever warrant the output quality cost of reaching for a RAG-like workaround (and the size of the context window is such that you shouldn't have the probems RAG-like workarounds mitigate very often anyway, and because the system prompt, long as it is, is very small compared to the context window, you have a very narrow band where shaving anything off the system prompt is going to meaningfully mitigate context pressure even if you have it.)
I can see something like that being a useful approach with a model with a smaller useful context window in a toolchain doing a more narrowly scoped set of tasks, where the set of situations it needs to handle is more constrained and so identify which function bucket a request fits in and what prompt best suits it is easy, and where a smaller focussed prompt is a bigger win compared to a big-window model like GPT-5.
There was also a paper I saw that went by that showed model performance went down when extra unrelated info was added, that must be happening to some degree here too with a prompt like that
Or they just choose Python because that's what most AI bros and ChatGPT users use nowadays. (No judging, I'm a heavy Python user).
The LLM has to know how to use the tool in order to use it effectively. Hence the documentation in the prompt.