Zod

import type { NextApiRequest, NextApiResponse } from 'next';
import z from 'zod';

type Data = {
  success: boolean;
  error?: string;
  data?: any;
};

const inputSchema = z.object({
  email: z.string(),
});

export default async function handler(
  req: NextApiRequest,
  res: NextApiResponse<Data>
) {
  try {
    const { email } = inputSchema.parse({ email: req.query.email });
    // you can be sure that 'email' is a string from here...
    res.status(200).json({ success: true });
  } catch (error: any) {
    return res.status(500).json({ success: false, error });
  }
}

Powerful validation options

const SUBSCRIPTIONS = ["HOBBY", "SCALER", "TEAM", "ENTERPRISE"] as const;
const SubscriptionEnum = z.enum(SUBSCRIPTIONS);

z.object({
  title: z.string().min(5),
  description: z.string().nullable(),
  countViews: z.number(),
  subscription: z.enum(SubscriptionEnum),
  tags: z
    .object({
      value: z.string(),
      label: z.string(),
      color: z.string(),
    })
    .array(),
});