import { Credentials } from './credentials.js';
export interface TokenValidationResult {
    success: boolean;
    credentials?: Credentials;
    error?: string;
}
/**
 * Check if the current token is valid.
 * If expired, returns an error prompting re-authentication.
 * No refresh is attempted here; callers decide whether to refresh or re-authenticate.
 */
export declare function ensureValidToken(): Promise<TokenValidationResult>;