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

Section:
3.5.2 eRoamingPullEVSEStatusById

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 up to 100 EVSEs by their EVSE Ids.
/// </summary>
/// <param name="ProviderId">The unique identification of the EVSP.</param>
/// <param name="EVSEIds">Up to 100 EVSE Ids.</param>
/// <param name="QueryTimeout">An optional timeout for this query.</param>
public async Task<HTTPResponse<IEnumerable<KeyValuePair<EVSE_Id, OICPEVSEStatus>>>>

    PullEVSEStatusById(EVSP_Id               ProviderId,
                       IEnumerable<EVSE_Id>  EVSEIds,
                       TimeSpan?             QueryTimeout = null)

{

    [...]

}

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

              PullEVSEStatusById(EVSP_Id.Parse("DE*GDF"),
                                EVSEIds:       Enumeration.Create(EVSE_Id.Parse("DE*GEF*E123456789*1"),
                                                                  EVSE_Id.Parse("+49*822*083431571*1")),
                                QueryTimeout:  TimeSpan.FromSeconds(120)).

              ContinueWith(task => {

                  var eRoamingEVSEStatusById = task.Result.Content;

                  if (eRoamingEVSEStatusById.StatusCode.HasResult)
                      Console.WriteLine(eRoamingEVSEStatusById.
                                            EVSEStatusRecords.
                                            Select(evsestatusrecord => "EVSE '" + evsestatusrecord.Id +
                                                                       "' has status " +
                                                                       evsestatusrecord.Status.ToString() +
                                                                       "'").
                                            AggregateWith(Environment.NewLine) +
                                            Environment.NewLine));

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

              });


req.Wait();