I realized I had actually read this one before but forgotten about it, so it was kinda like getting to experience it twice. I found myself reminiscing about For a Breath I Tarry and The Star, hence the prompt.
I get it mixed up with Sturgeon's "The Nail and the Oracle."
I dunno. Clarke told this story as "any technology sufficiently advanced is indistinguishable from magic." It gets bonus points for being the first real singularity tale but it's always struck me as painfully unimaginative.