/**
 * Outbound attachment preparation — pure, no MCP or SMTP dependency.
 *
 * Stats every file BEFORE anything is read into memory, and enforces the
 * configured cap against the base64-ENCODED size (raw × 4/3), because that is
 * what the SMTP server actually receives; a 20 MB file inside a 25 MB limit
 * still bounces as ~27 MB on the wire. Rejections list every file with its
 * size so the caller can see exactly what to trim instead of decoding an
 * opaque SMTP 552 later.
 */
import type { AttachmentMeta } from '../types/index.js';
/** An attachment request: a bare path, or a path with inline/cid metadata. */
export interface AttachmentInput {
    path: string;
    /** Override the filename shown to the recipient (default: basename). */
    filename?: string;
    /** Content-ID — the HTML body references the file as src="cid:<cid>". */
    cid?: string;
    /** Explicit MIME type when the extension would misdetect. */
    contentType?: string;
}
export interface PreparedAttachment {
    filename: string;
    path: string;
    size: number;
    cid?: string;
    contentType?: string;
}
export interface PreparedAttachments {
    attachments: PreparedAttachment[];
    totalBytes: number;
    totalEncodedBytes: number;
}
export declare function formatSize(bytes: number): string;
/**
 * Render an email's attachment list for a tool response.
 *
 * The part id is the point. `download_attachment` accepts a filename or a
 * partId and tells the caller to read partIds from `get_email`, but nothing
 * ever printed them — and for the case the docs single out, inline `cid:`
 * images, the filename selector cannot work at all: such parts rarely carry a
 * name parameter, so extractAttachments falls back to 'unnamed' and every one
 * of them collides. The cid is shown for the same reason, since that is what
 * an `<img src="cid:…">` in the body refers to.
 */
export declare function describeAttachments(attachments: AttachmentMeta[]): string;
export declare function prepareAttachments(paths: (string | AttachmentInput)[], maxTotalMb: number): Promise<PreparedAttachments>;
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