Charles Schwab is one of the most respected financial services firms in the world. Our UX / content team was responsible for enhancing the digital trading experience. This flow introduces clients to a new Watchlist. 
Environments: Desktop, Mobile web & application
Design principle: "Know as you know."
Testing methods: A/B, UAT
Role: Content Strategy Lead  
Initial desktop view - Welcome to watchlist message
I've added a symbol to watchlist. 
Here, I can create a new watchlist or edit this one.
Oops. I added a bad character. So, let's give the client information to continue instead of a scolding. 
Errors happen. So, let's provide corrective details. 
Disruptive actions: We give the clients choice.