How to use Moodle webservices

Hello, I'm new to moodle's webservices and I wish to try creating a course via the core_course_create_courses function.

I'm calling the webservice with the following url and its giving me an error, can someone help me out here please.

uri: http://localhost/moodle/webservice/rest/server.php?wstoken=d0b8004660ba1144f8af3e8478ec6b01&moodlewsrestformat=json&wsfunction=core_course_create_courses

error: 

{"exception":"invalid_parameter_exception","errorcode":"invalidparameter","message":"Invalid parameter value detected"}

I'm unable to understand the cause of the error its saying the a parameter has an invalid value but which one? and why?