Custom Entity with Regex Pattern can be used to validate customer input in Salesforce Einstein BOT.

1. Create a Custom Entity. Use the Regex Pattern to validate the customer input. In the following example, I have used \d{9} which means the customer should enter 9 digit number.

2. In the Dialog, you can use Question to get the customer input. For “Expected response format”, use the Custom Entity. Configure “Repairing Misunderstanding” to show text when the customer input is not matching with the Regex Pattern defined in the Custom Entity.

Output: