import type { OpenRouterPlugin } from '../types';
/**
 * Example plugin that replaces the default CostTracker with an extended version.
 * This extended version could, for example, push usage/cost data to an external billing service.
 */
export declare function createBillingCostTrackerPlugin(billingOptions?: {
    apiEndpoint?: string;
    apiKey?: string;
}): OpenRouterPlugin;