/**
 * Query parameter that routes a webhook to a local subscription key.
 *
 * @experimental
 */
export declare const MCP_EVENT_CALLBACK_KEY_PARAM = "mcp_event_subscription";
/**
 * Validate a webhook callback URL.
 *
 * https is required. http is allowed only for `127.0.0.1` and `[::1]` when
 * `allowInsecureLocalhost` is set. Credentials, fragments, and an existing
 * `mcp_event_subscription` parameter are rejected.
 *
 * @experimental
 */
export declare function validateCallbackUrl(url: string, opts?: {
    allowInsecureLocalhost?: boolean;
}): URL;
/**
 * Append `mcp_event_subscription=<key>` to a validated callback URL.
 *
 * @experimental
 */
export declare function withCallbackKey(url: URL, key: string): string;
/**
 * Read the subscription key from a callback URL.
 *
 * @experimental
 */
export declare function readCallbackKey(url: string): string | undefined;