Mongoose OS RPC MQTT commands

I’m using a ESP32 firmware on Mongoose OS which uses a RPC protocol .
An example format from a publish command is as follows

mosquitto_pub -h mythbox -t esp32_8AD88C/rpc -m ‘{“method”:“relay”,“args”:{“name”:“RELAY3”,“cmd”:“ON”}}’

Question how do I code a “thing” for this …?
something like this???
How do I put a JSON string in the ON/OFF commands?

Type switch : hotwater_booster_switch "Hotwater Booster" [commandTopic="cmd/RELAY3", on="{"method":"relay","args":{"name":"RELAY3","cmd":"ON"}}'", off="{"method":"relay","args":{"name":"RELAY3","cmd":"OFF"}}'" ]

Looks promising.
Your commandTopic doesn’t seem to match your example.

A problem is the on/off parameters require a quoted string
which gives you problems if you want to send
including the quote marks.
You have to hide (escape) those internal quote marks

I’m not sure if using alternate single quote marks may work in this context to make it more legible for humans
don’t think that works in a xx.things file though.