def job_description(jobs):
    """Return description of jobs for usage string.
    """
    job_last = len(jobs) - 1
    if job_last <= 0:
        return '', -1
    job_list = 'Jobs:\n'
    for j, descr in enumerate(jobs):
        job_list += ' {:3d} {}\n'.format(j, descr)
    return job_list, job_last
