Your objective statement tells the agent what number to minimize or maximize. In the default program.md, it's one line: "get the lowest val_bpb."
That's it. No paragraph of context. No explanation of what val_bpb means. The agent already knows because it reads prepare.py and train.py. Your objective statement should be equally direct. One metric. One direction. If you find yourself writing a paragraph to explain your goal, you probably have more than one goal. Pick one.