The service description can be found in the OICP 2.1 (EMP).

Section:
3.5.1 eRoamingPullEVSEStatus

To download the latest OICP Version, please visit our website:
https://www.hubject.com/downloads/

/// <summary>
/// Create a new task requesting the current status of all EVSEs (within an optional search radius and status).
/// </summary>
/// <param name="ProviderId">Your e-mobility provider identification (EMP Id).</param>
/// <param name="SearchCenter">An optional geo coordinate of the search center.</param>
/// <param name="DistanceKM">An optional search distance relative to the search center.</param>
/// <param name="EVSEStatus">An optional EVSE status as filter criteria.</param>
/// <param name="QueryTimeout">An optional timeout for this query.</param>
public async Task<HTTPResponse<IEnumerable<KeyValuePair<EVSE_Id, OICPEVSEStatus>>>>

    PullEVSEStatus(EVSP_Id          ProviderId,
                   GeoCoordinate    SearchCenter      = null
                   Double           DistanceKM        = 0.0,
                   OICPEVSEStatus?  EVSEStatusFilter  = null
                   TimeSpan?        QueryTimeout      = null)

{

    [...]

}

var req = new EMPClient("api.playground.hubject.com").

              PullEVSEStatus(EVSP_Id.Parse("DE*GDF"),
                             SearchCenter:     new GeoCoordinate(Latitude. Parse(49.731102),
                                                                 Longitude.Parse(10.142533)),
                             DistanceKM:       100,
                             EVSEStatusFilter: OICPEVSEStatusType.Available,
                             QueryTimeout:     TimeSpan.FromSeconds(120)).

              ContinueWith(task => {

                  var eRoamingEVSEStatus = task.Result.Content;

                  if (eRoamingEVSEStatus.StatusCode.HasResult)
                      Console.WriteLine(eRoamingEVSEStatus.
                                            OperatorEVSEStatus.
                                            Select(evsestatus => "'" + evsestatus.OperatorName +
                                                                 "' has " +
                                                                 evsestatus.EVSEStatusRecords.Count() +
                                                                 " available EVSEs").
                                            AggregateWith(Environment.NewLine) +
                                            Environment.NewLine));

                  else
                  {
                      Console.WriteLine(eRoamingEVSEStatus.StatusCode.Code);
                      Console.WriteLine(eRoamingEVSEStatus.StatusCode.Description);
                      Console.WriteLine(eRoamingEVSEStatus.StatusCode.AdditionalInfo);
                  }

              });

req.Wait();