import click

def transform_data(paths): ...
def save_result(data, path): ...

@click.command()
@click.argument('output-path')  # first argument
@click.argument('input-paths', nargs=-1)  # all other arguments
def cli(output_path, input_paths):
    result = transform_data(paths=input_paths)
    save_result(data=result, path=output_path)

if __name__ == '__main__':
    cli()