Olo can send down a discount to Toast POS if a discount is configured correctly in Toast. Once the Discount is created in Toast, it can be linked in Olo using the GUID generated by Toast. At this time (2/22/2018), Olo can only send an Open Dollar, Order Level Discount to Toast, so it will need to be configured as such in Toast. Below is a screenshot of how the discount needs to be configured in Toast.
Once the discount has been created in Toast, you can create desired discount in the Olo Dashboard. Once the discount is created in the Olo Dashboard, let your Olo Technical Account Manager know the name of the Discount, and they will get the Discount linked to Toast. Toast does not show the GUID required through their website at this time.