The caller needs to construct a valid request.

MY_API_KEY = abcd1234efgh  # obtained through the user's Indigo account
MY_REFLECTOR = "someReflectorID"  # the name of the user's server machine on their Indigo account
PLUGIN_ID = "com.something.myPlugin"
ACTION_ID = "handle_message"  # The ID from Actions.xml (not an Action object ID number)

# The payload must be valid JSON. The API does not support binary encoding and payloads should by of a reasonable size.
payload = {
    "someKey": "some string value",
    "someOtherKey": 12345678,
    "someDict": {"foo": 123, "bar": "abc"}
}

my_url = https://MY_REFLECTOR.indigodomo.net/message/PLUGIN_ID/ACTION_ID/?other=payload&api-key=MY_API_KEY

my_url will contain the response of a successful call (if the action returns a response) or an error if the call was unsuccessful (error codes above). Using the above example, the resonse will include 24,691,356 or “someOtherKey” * 2.