/** Maximum UTF-8 payload size for a human-authored message. */
export declare const HUMAN_MESSAGE_TEXT_MAX_BYTES: number;
/** Returns the encoded UTF-8 size used by the message API. */
export declare function messageTextUtf8ByteLength(value: string): number;
/** Whether human-authored message text fits the API's UTF-8 byte budget. */
export declare function isHumanMessageTextWithinLimit(value: string): boolean;