Free and Flat Rates

Adding a simple Fat Rate in Decimal is easy. In the top block, simply add this (make sure it is valid JSON, with a comma before and after):

"Flat": {
    "enabled": true,
    "services": [
        {
            "code": "STANDARD_SHIPPING",
            "total_price": 2000
        }
    ]
},

You will now have a new rate; however, if you click Save and check for rates, you will see "Unknown Service".

To fix this, you can -

EITHER set the "display_text" property directly on the rate like this:

"Flat": {
    "enabled": true,
    "services": [
        {
            "code": "STANDARD_SHIPPING",
            "total_price": 2000,
            "display_text": "Standard Shipping"
        }
    ]
},

OR if you add a "rate_mapping" property then you can map any rate code to a display text (If the "display_text" property is set, then the "rate_mapping" will be ignored):

"rate_mapping": [
    {
        "carrier": "Flat",
        "services": {
            "STANDARD_SHIPPING": "Standard Shipping"
        }
    }
]

To make this rate as Free Shipping, simply set total_cost to 0.

Cheapest Rate

Decimal has a special property called "cheapest". Sometimes, rather than add a Free or Flat rate, you want the cheapest rate to be modified to Free, or even to a Flat Rate, such as '$5 shipping'. You can get this modified rate by adding the "cheapest" property

"cheapest": {
    "total_price": 0,
    "display_text": "Free Shipping"
}

The cheapest rate will now always have its price modified to 0 and display text changed to "Free Shipping".

If you're wondering how to set this rate to only apply above a certain cart total for example, you can find the answer in the Conditions section.