Some Oracle data dictionary help...

To get parameters information for your functions/procedures/packages etc. you can use all_arguments view. A sample query is attached...

select owner, object_name, package_name, argument_name, position, data_type, in_out
from all_arguments
where owner = (case when lc_user is null then user else lc_user end)
and package_name = (case when lc_pkg_nm is null then package_name else lc_pkg_nm end)
order by owner, package_name, object_name, position;

Further another view called all_source is also pretty useful if you have to look at the actual source code of a component.

Following links helped me on this -

1. http://www.eveandersson.com/writing/data-model-reverse-engineering#plsql
2. http://www.c-sharpcorner.com/Forums/ShowMessages.aspx?ThreadID=48498