import { z } from 'zod';
/**
 * An optional string schema that converts empty strings to `undefined`.
 * LLMs often send `""` for optional fields instead of omitting them,
 * which causes the Todoist API to reject the request.
 *
 * `.optional()` must be outermost so the field stays optional in `z.infer` output types.
 */
export declare function optionalString(description: string): z.ZodOptional<z.ZodPipe<z.ZodString, z.ZodTransform<string | undefined, string>>>;
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