Ask HN: What are good chatbot app that can use tools?

i have subs to chatgpt, grok, claude, and right now they are indeed very useful, esp when im on the go on mobile. But the one thing they still dont do is that they can't write/read my data the way i want it.

What are some good opensource projects where I can have the exp of these paid apps but that can actually CRUD w/ my data? That has a good ios app?

Or if we are going selfhosting route, whats your stack?