Starting Runbook via Azure API, Portal, or ISE Add-On yields “input parameter type mismatch” error

[JoeBrockhaus]

Described on StackOverflow here.

Given a simple runbook:

workflow test
{
    [CmdletBinding()]
    param([string] $NumericString)

    write-output $NumericString
}

When starting it with a numeric value (ie: 5) via the Azure Portal as a new Job (published), via the Test Pane, or using the Azure Automation PowerShell ISE Add-On, the following error is returned and the execution Fails.

The values provided for the root activity's arguments did not satisfy the root activity's requirements: 'DynamicActivity': Expected an input parameter value of type 'System.String' for parameter named 'Numeric'. Parameter name: rootArgumentValues

This appears to be something the API is handling strangely, as the JSON that is passed contains valid string data for the property, but it is being interpreted incorrectly and requires extra quote escaping to work.