I have a flexible schedule in the next 6 months and I normally use google flight to look for the lowest cost flight. It works well for round trip flights because it shows the prices on each date, but it doesn't work for multi city flights. For example, I was looking for the following flights:

yyz->opo
lis->yyz

I found the dates for the cheapest direct flight for each segment, but when I use those for a multi city flight it is no longer the cheapest. I am using the multi city flight tool and manually try different date combinations to come up with the best flight. Is there a better way? Any AI tool that can help?