export interface ImageValidationResult {
    valid: boolean;
    contentType?: string;
    contentLength?: number;
    error?: string;
}
/**
 * Validates an image URL by performing a HEAD request.
 * Checks:
 * - HTTP status is 2xx
 * - Content-Type starts with "image/"
 * - Content-Length is less than 5MB (5242880 bytes)
 *
 * @param url - The image URL to validate
 * @param timeoutMs - Request timeout in milliseconds (default: 5000)
 * @returns ImageValidationResult with validation details
 */
export declare function validateImageUrl(url: string, timeoutMs?: number): Promise<ImageValidationResult>;