Apptoto's APIs currently only support HTTP Basic Authentication.
Each request to our API should include an "Authorization" header that contains the word Basic followed by a space and a base64-encoded string username:api_key .
For example:
Authorization: Basic EGVtbzpwQDU2dzByZB==
You can find your "API Key" listed on the "Settings" > "Integrations" > "API" tab in the Apptoto web portal.