Output of tool.execute is typed incorrectly or gives errors

The return type of tool.execute now includes ValidationError to handle validation failures. You must narrow the result type before accessing output schema properties to satisfy TypeScript's type checking.

Property 'fullName' does not exist on type 'ValidationError<any> | { fullName: string; }'.
Property 'fullName' does not exist on type 'ValidationError<any>'.ts(2339)

import { createStep } from '@mastra/core/workflows';
import { z } from 'zod';
import { createTool } from '@mastra/core/tools';

const fullNameOutputSchema = z.object({
  fullName: z.string(),
});

const fullNameFinderTool = createTool({
  id: 'full-name-finder',
  description: 'Finds a full name',
  inputSchema: z.object({
    firstName: z.string(),
  }),
  outputSchema: fullNameOutputSchema,
  execute: async (inputData) => {
    return {
      fullName: `${inputData.firstName} von der Burg`,
    };
  },
});

export const testStep = createStep({
  id: 'test-step',
  description: 'description',
  inputSchema: z.object({
    firstName: z.string(),
  }),
  outputSchema: fullNameOutputSchema,
  execute: async ({ inputData }) => {
    const result = await fullNameFinderTool.execute({ firstName: inputData.firstName });

    if ('error' in result && result.error) {
      console.error('Validation failed:', result.message);
      console.error('Details:', result.validationErrors);
      return;
    }

    return {
      fullName: result.fullName,
    };
  },
});