The key request header information used with the Pacejet API includes the PacejetLocation, PacejetLicenseKey, and Content-Type. The PacejetLocation is a unique identifier (e.g. DemoAPI) representing one database of shipping data, carrier account settings, and other information. The PacejetLicenseKey is specific to a PacejetLocation, provides authorization to use the API, and may change if it expires or is re-issued by Pacejet. The Content-Type will generally be application/json since that is the recommended content format to use with the Pacejet API.
See examples of request header information using the API | Samples page for an endpoint such as ConfirmsList. Notice the sample code settings for PacejetLocation, PacejetLicenseKey, and contentType. Another way to browse header examples is to view the Google Chrome developer tools area, run a request with samples, and browse the network / headers tab as shown below.