Requested data from the APIs is returned as a JSON object. A succesful response looks like this:

{
    "status": true,
    "credits": 80963,
    "airport": {
        "id": "EHVK",
        "name": "Volkel Air Base",
        "city_name": "Uden",
        ...
    },
    "metar": {
        "id": 261742709,
        "cavok": false,
        "ceiling": 6400,
        ...
    },
}

The status attribute is always true in case of a succesful request.
The remaining number of credits for your account can be found in credits. This way you can keep track of how many calls there are left.

Errors

In case of an error, the result will look like this:

{
    "status": false,
    "message": "Invalid locale (err:4)",
}

The status attribute is always false.
The error message can be found in message.