For authenticating APIs made to Doctor Droid for sending events, you need to obtain an API key. You can signup for a free account (no credit card or payment needed) and work with up to 100K per month.
Once you signup, you can start navigating the tool and setup monitors over sample events pre-created by us (you can delete them later). You will receive an email for verification. Once you verify the email by clicking on the link, you will be able to see your API Key. That Key is needed to be passed in the header for each Ingestion API request.