To calculate directions between two coordinates via a third coordinate, use the CalculateRouteRequest service and specify the start (waypoint0), middle point (waypoint1) and destination (waypoint2). Specifying waypoint1 as stopOver instead of passThrough results in breaking the journey here, not just driving through. The string geo! indicates that you are specifying each point using latitude and longitude.

Note that you also have to specify an apiKey to authenticate. For more information on authentication, see the Identity & Access Management Developer Guide.

The following example requests the fastest route for a car without taking traffic conditions into account from the Westin Grand hotel at Unter den Linden in Berlin (52.516858379, 13.3884717) to the Staatsoper in Berlin (52.51733824, 13.394678415) via the Deutsche Guggenheim (52.51704771, 13.39131492). 

https://route.ls.hereapi.com/routing/7.2/calculateroute.json
?apiKey={YOUR_API_KEY}
&mode=fastest;car;traffic:disabled
&waypoint0=geo!52.516858379,13.3884717
&waypoint1=geo!stopOver!52.51704771,13.39131492
&waypoint2=geo!52.51733824,13.394678415
Note: This example uses a HERE API Key to authenticate your request. For the available authentication options, see the Identity & Access Management Developer Guide.