How to indicate the "purpose" of each csv?

The create assistant API allows to specify multiple files. Let’s say I want to create a data processing/visualization assistant and specify multiple CSVs, each containins different structured data. How can I indicate the “purpose” of each CSV?

assistant = client.beta.assistants.create(instructions=prompt,
tools=[{ “type”: “code_interpreter” }],
file_ids=[ for file in <my_csv_files>]