(API) is An application programming interface that implemented in order to allow other software or websites to interact with it, defined set of (HTTP) request messages along with a definition of the structure of response messages.

To extract the original URL you can send a request to http://gofast.hunikal.com like http://gofast.hunikal.com/api/?url=http://1tool.biz/188603 and the result will be plan text as "http://www.4shared.com/file/62269696/83a6e334/Kasas_El-Quran_Amr-Khaled-E08.html"

You can send the request and get the result as XML format or Plain Text format

The API also provide further details in the result as it might provide the error that can occur during the extraction, and this is a list of the possible error that might come up:
0: Invalid URL
1: Unsupported Website
2: Error in the URL
3: cann't find the original URL

For more advanced request:
you can define the format of the result as Plain Text or XML format using the argument "format" and send the request

To extract in plain text format:
To extract in XML format: