Gen1 mqtt message payload

Hello,

We are planning to use Shelly 3EM for metering and are planning to read data via MQTT, because the rest of our system is also implemented via MQTT.

I've found the Gen1 API, where I can see the topics on which shelly reports the data to but payload structure is not present. We are at the moment still waiting for our shipment to arrive, but would already like to start implementing it in our service.

I see that the Gen2 API documentation is good but Gen1 are lacking in a lot of ways.

Are there any other documentations or examples anywhere where the payload body is visible?