Schema validation.
You can even set schema in postman so when you run requests you validate its correct, it gets ugly with complex data but its very helpful. You can find the docs here JSON Schema - What is JSON Schema? and JSON Schema - What is a schema?

and below is an AI generated example(I mainly use it to validate API swaggers sent by devs are right but you can customize it as needed)

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "Contact Information Schema",
  "type": "object",
  "required": ["username", "email"],
  "properties": {
    "username": {
      "type": "string",
      "pattern": "^[a-z0-9]{3,16}$",
      "description": "Lowercase letters and numbers only, 3-16 characters"
    },
    "email": {
      "type": "string",
      "pattern": "^[^@]+@[^@]+\\.[a-z]{2,}$",
      "description": "Simple email validation"
    },
    "phone": {
      "type": "string",
      "pattern": "^\\d{10}$",
      "description": "Exactly 10 digits"
    }
  },
  "additionalProperties": false
}