@cyril.jean for completeness, here the way to parse the input using the xpath parser
[[inputs.mqtt_consumer]]
...
data_format = "xpath_json"
xpath_native_types = true
[[inputs.mqtt_consumer.xpath]]
metric_name = "/name"
timestamp = "/timestamp"
timestamp_format = "unix_ms"
field_selection = "/fields/*"
tag_selection = "/tags/*"
