/**
 * A tool error that is reported back to the MCP client as a tool result with
 * `isError: true`. Always carries a machine-readable code and a repair hint so
 * that the model can correct its call.
 */
export declare class McpToolError extends Error {
    code: string;
    hint?: string | undefined;
    constructor(code: string, message: string, hint?: string | undefined);
    toJSON(): {
        error: {
            code: string;
            message: string;
            hint: string | undefined;
        };
    };
}
/**
 * Map an arbitrary error (e.g. a failed upstream fetch) to a tool error.
 */
export declare function toToolError(e: unknown): McpToolError;