To add custom tags to a device use the below config:
# ================================== General ===================================
# The name of the shipper that publishes the network data. It can be used to group
# all the transactions sent by a single shipper in the web interface.
# If this options is not defined, the hostname is used.
#name:
# The tags of the shipper are included in their own field with each
# transaction published. Tags make it easy to group servers by different
# logical properties.
tags: ["service-X", "web-tier"]