export declare class McpIdempotencyStore {
    private static readonly store;
    static digest(caller: string, tool: string, args: unknown): string;
    static scopedKey(caller: string, header: string): string;
    static get(key: string): unknown | undefined;
    static getStatus(key: string): number | undefined;
    static set(key: string, payload: unknown, status?: number): void;
    static reset(): void;
    private static sweepExpired;
    private static enforceCap;
}