Identify Api Identification Structure

{
  "$schema": "https://json-structure.org/meta/core/v0/#",
  "$id": "https://raw.githubusercontent.com/api-evangelist/amplitude/refs/heads/main/json-structure/identify-api-identification-structure.json",
  "name": "Identification",
  "description": "Identification schema from Amplitude Identify API",
  "type": "object",
  "properties": {
    "user_id": {
      "type": "string",
      "description": "A readable ID specified by you. Required unless device_id is present."
    },
    "device_id": {
      "type": "string",
      "description": "A device-specific identifier. Required unless user_id is present."
    },
    "user_properties": {
      "type": "object",
      "description": "An object containing user property operations. Each key is an operation type and the value is an object of property names to values.",
      "properties": {
        "$set": {
          "type": "object",
          "description": "Set the value of a user property. If the property already exists, the value is overwritten.",
          "additionalProperties": true
        },
        "$setOnce": {
          "type": "object",
          "description": "Set the value of a user property only if it has not already been set. Useful for properties like initial_referrer.",
          "additionalProperties": true
        },
        "$add": {
          "type": "object",
          "description": "Increment a numeric user property by the specified value.",
          "additionalProperties": {
            "type": "double"
          }
        },
        "$append": {
          "type": "object",
          "description": "Append a value or values to a list user property.",
          "additionalProperties": true
        },
        "$prepend": {
          "type": "object",
          "description": "Prepend a value or values to a list user property.",
          "additionalProperties": true
        },
        "$unset": {
          "type": "object",
          "description": "Remove a user property by setting its value to the string $unset.",
          "additionalProperties": true
        },
        "$remove": {
          "type": "object",
          "description": "Remove a value from a list user property.",
          "additionalProperties": true
        }
      }
    }
  }
}