I've started using DNSControl for configuring DNS for my personal domains and it's been delightful. Declarative DNS!
I get comments (the DSL is just JS), history (it's in git) and trivial rollback! I've switched my DNS provider to Hetzner (which is free!) to use this.
There's something pleasingly self-referential about configuring an agent by talking to it.
> Remember that [fact about data formats].
Agent: Noted.
... realise nothing happened ...
> Write to your rules file that when I say "remember", I want you to write to the rules file.
I tend to shy away from automatic, implicit behaviour in software. I've seen CMake setups where FindFoo.cmake is automatically picked up for configuring the Foo library.
What are examples of tools with a larger amount of automagic behaviour that you like?