SendGrid User Authorization from iOS App

Question

I am trying to add email contact to my SendGrid Account List, but am unable to authenticate from the iOS App. I have tried authentication from https://sendgrid.com/docs/API_Reference/Web_API_v3/How_To_Use_The_Web_API_v3/authentication.html but getting 404 NOT Found Error. To add contact to a list, I need to hit https://sendgrid.com/docs/API_Reference/Web_API_v3/Marketing_Campaigns/contactdb.html#Add-a-Single-Recipient-to-a-List-POST API referenced here, but its returning "Authentication Required".

Answer 1

Got it. Answer to my question is SendGrid API v3 Documentation i.e. https://sendgrid.com/docs/API_Reference/api_v3.html. Need to send the API key in request headers.