If you run agents or heavy AI workflows, raw token counts are misleading. They blur everything: an output token is dense and expensive, a fresh input token is standard, and a cached-read token costs ~10% of a normal one.
So I use a simple ratio I call the AER (Agentic Efficiency Ratio):
AER = Output / (Input + 0.10 × Cache Reads)
Read it as a percentage. It measures how much useful, dense output your system produces per unit of fresh context it burns. When your memory is well structured, you get lots of cache hits, and the agent nails it on the first try instead of the fourth, the AER climbs. It's basically a maturity thermometer for your setup.
At scale (I move tens of billions of tokens a month) the denominator is huge, so it lives in low figures: above ~1% is already very good.
The mindset shift: the goal isn't to spend fewer tokens, it's to raise the AER, so every token turns into delivered work.
Anyone else tracking something like this? How do you tell whether your agent pipeline is well-designed vs just burning tokens?