We already include information for a ride like how long it is, how much elevation gain there is and how long it took for the original rider to film it, but actually explaining how hard a ride is isn't an easy thing to do.
Quoting average gradient or maximum gradient only works if it's a long, more or less constant climb. That's fine for mountains but not much use for every other ride.
Existing ways to express the effort required (TSS, Suffer Score etc) are an amount of work undertaken by someone to do a session. You can get a high TSS score on a flat road if you go hard enough, so that approach doesn't work either.
That's why we created the toughness score. It’s a formula that first accounts for the time taken to do the ride, then adds up the time spent at each gradient. It takes longer to get up a 10% slope than it does to get down it, so an undulating ride will still score highly if it has some steep or long climbs in it.
You can filter by toughness score on the FulGaz website