The structure depends on a number of elements: link, private key, public key and information body. You must do post request to https://<your_subname>.elmasys.com/api/api/k/<private_key> link with body parameters.

{
    "private": "<private_key>",
    "group": "<function_group_name>",
    "function": "<function_name>",
    "parameter_name1": "<parameter_value1>",
    "parameter_name2": "<parameter_value2>"
}

As a result, you will get 200 status (if everything is right).
And JSON:
If something not true or not valid you get:
{"success": 0, "message": "", "error": "Something is not right"}
If success = 1, then everything is right.

For example you can add measurement unit.

{
    "success": "1",
    "message": "",
    "error": ""
}

For get integration and authorisation details, please fill free to contact with us.
We configure for you sandbox for your tests. And we will help with integration.

For API Structure please go by link.
For Authorisation you must have Private key and Public Key. For get Private key and Public Key fir tests please connect with us.
So, when you try to do request. You can get this responses:

{
    "success": "0",
    "message": "Sucsses!",
    "error": ""
}

{
    "success": "0",
    "message": "",
    "error": "Private key is not set"
}