When the API_TYPE argument is set to "aws-forecast", API_Request in-database function works with Amazon Forecast. The syntax is:
SELECT * FROM tapidb.API_Request(
ON { table | view | (query) } [ AS InputTable ]
USING
AUTHORIZATION('{"AccessId": "AWS_access_id",
"AccessKey" :"AWS_Access_Key",
"Session_Token": "AWS_Session_Token",
"Region" : "aws_region"}')
ENDPOINT('forecast-endpoint')
API_TYPE('aws-forecast')
) AS alias;