If anyone's looking for something a bit more minimal, I can't recommend hax [0] enough. No MCP, agent just gets a shell tool, simple config, whole thing's in C.
I'm not sure, to be honest -- I think the main agent loop, tools, etc. are fairly standard and the main draw is fast start-up time, but it does have a very minimal default system prompt too.
ltrg · · focus · HN ↗
[0] <a href="https://usehax.dev/" rel="nofollow">https://usehax.dev/
exe34 · · focus · HN ↗
ltrg · · focus · HN ↗