The KellPro API uses HTTP Basic Authentication. All requests should use HTTPS to protect your API key.
You can try a simple API call via cURL to test your settings.
curl -u [API Key]: "https://api.kellpro.com/v2/odcr/courts"
Creating the Authorization Header
In most programming languages, the API key can be specified in the authentication header and is automatically encoded as a Base-64 string containing the username and password.
The KellPro API requires that your key be set in the username section of the header. If your library requires that a password be set as well, you can set it to an empty string, or any short string of characters.