Interface MessageAttachment

A file the turn PRODUCED (create_spreadsheet / create_document), carried structurally on the reply (0.54.0). url is a 7-day capability URL — the same link the reply text contains — so a host can render a download affordance without parsing prose the model may rewrite or drop.

interface MessageAttachment {
    fileId: string;
    fileName: string;
    mimeType: string;
    url: string;
}