The vda5050_msgs package contains the datatypes (json objects) specified by the VDA "Arbeitskreis Schlüsseltechnologien" in their recommondation "VDA 5050 - Schnittstelle zur Kommunikation zwischen Fahrerlosen Transportfahrzeugen (FTF) und einer Leitsteuerung. This package provides the message files which can be used to be (de-)serialized with an implementation of mqtt (e.g mqtt_bridge) or to plain json (rospy_message_converter) or similar.
https://github.com/ipa320/vda5050_msgs/blob/1d7f761e72abe2b487bcae0f74a9873750ca5f93/msg/AGVPosition.msg#L22