This is a good and clever benchmark and a worthy successor to the previous two. That being said, I find that the "No tools" approach is a bit odd. They're basically saying that it's OK to have tools as long as they're hidden behind the API layer. Isn't this an odd line to draw?

It feels like it should be about having no ARC-AGI-3-specific tools, not "no not-built-in-tool"...