Currently, there is no level 100 in the Story games (other than Dragon - I think?), they were designed with the intention of level 99 being the top/last level.
In the past, a few very dedicated and amazing players have gotten enough XP to reach 100 but as soon as they do, their games essentially no longer work. When this happens they have to contact the team who then have to go into the player's account and alter their XPs just to ensure they can continue to access their game.
The last time I recall seeing this happening was back in January and I think the team went and raised the XP requirements to reach level 100 even higher than it already was in order to try and prevent this from happening to as many players as possible. Keeping all that in mind, if you ever find yourself getting within a few hundred points of reach level 100, you'll likely have to contact the team to try and prevent the level 100 glitch from closing your game.