The code is based on the ErrorDescription library.
Library contains ErrorDescription() function with two input parameters error_code and optional parameter txt_prefix.
string ErrorDescription(int error_code,string txt_prefix="")
GetLastError() return codes can be found here
OrderSend() function’s retcode field values can be found in
Both tables are included in ErrorDescription() function.
LibraryTest.mq5 script can be used to check description of a known error code. Just execute script with an input error_value set to error code and it will print description. If error_value is set to -1 script will print all available error codes.