This is the result from a request to AGOL for a line record. The last 2 lines are the features and geometry.
This one I added in the editor on AGOL
{"objectIdFieldName":"OBJECTID","uniqueIdField":{"name":"OBJECTID","isSystemMaintained":true},"globalIdFieldName":"GlobalID",
"geometryProperties":{"shapeLengthFieldName":"Shape__Length","units":"esriMeters"},
"geometryType":"esriGeometryPolyline","spatialReference":{"wkid":102100,"latestWkid":3857},
"fields":[{"name":"RECORD_ID","type":"esriFieldTypeInteger","alias":"RECORD_ID","sqlType":"sqlTypeOther",
"domain":null,"defaultValue":null},{"name":"DATE_TIME","type":"esriFieldTypeDate","alias":"DATE_TIME",
"sqlType":"sqlTypeOther","length":0,"domain":null,"defaultValue":null},{"name":"SPEED","type":"esriFieldTypeDouble",
"alias":"SPEED","sqlType":"sqlTypeOther","domain":null,"defaultValue":null},{"name":"HEADING","type":"esriFieldTypeDouble",
"alias":"HEADING","sqlType":"sqlTypeOther","domain":null,"defaultValue":null}],
"features":[{"attributes":{"RECORD_ID":1,"DATE_TIME":1546359300000,"SPEED":1,"HEADING":12},
"geometry":{"paths":[[[-5871083.00245447,6028331.87508284],[-5871713.60793782,6027605.72331413]]]}}]}
This one I added using python. You will notice that it does not have any geometry.
{"objectIdFieldName":"OBJECTID","uniqueIdField":{"name":"OBJECTID","isSystemMaintained":true},"globalIdFieldName":"GlobalID",
"geometryProperties":{"shapeLengthFieldName":"Shape__Length","units":"esriMeters"},
"geometryType":"esriGeometryPolyline","spatialReference":{"wkid":102100,"latestWkid":3857},
"fields":[{"name":"RECORD_ID","type":"esriFieldTypeInteger","alias":"RECORD_ID","sqlType":"sqlTypeOther",
"domain":null,"defaultValue":null},{"name":"DATE_TIME","type":"esriFieldTypeDate","alias":"DATE_TIME"
,"sqlType":"sqlTypeOther","length":0,"domain":null,"defaultValue":null},{"name":"SPEED","type":"esriFieldTypeDouble",
"alias":"SPEED","sqlType":"sqlTypeOther","domain":null,"defaultValue":null},{"name":"HEADING","type":"esriFieldTypeDouble",
"alias":"HEADING","sqlType":"sqlTypeOther","domain":null,"defaultValue":null}],
"features":[{"attributes":{"RECORD_ID":18790232,"DATE_TIME":1547054436000,"SPEED":9.15513190909996E-07,"HEADING":20.2115876610467}}]}