curl --request POST \
  --url https://realtime-api.voiceflow.com/v1/stable/message/<messageID>/variant \
  --header 'Authorization: Bearer <token>'
  --header 'Content-Type: application/json' \
  --data '{
  "text": "<string>",
  "delay": 0,
  "condition": {
    "type": "value-variable",
    "matchAll": true,
    "assertions": [
      "<StableConditionAssertion>"
    ]
  }
}'

const response = await fetch('https://realtime-api.voiceflow.com/v1/stable/message/<messageID>/variant?projectID=<projectID>&environmentAlias=<environmentAlias>', {
  method: 'POST',
  headers: {
    Authorization: 'Bearer <token>',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    "text": "<string>",
    "delay": 0,
    "condition": {
      "type": "value-variable",
      "matchAll": true,
      "assertions": [
        "<StableConditionAssertion>"
      ]
    }
  }),
});
const data = await response.json();

import requests

response = requests.post(
    'https://realtime-api.voiceflow.com/v1/stable/message/<messageID>/variant?projectID=<projectID>&environmentAlias=<environmentAlias>',
    headers={'Authorization': 'Bearer <token>'},
    json={
      "text": "<string>",
      "delay": 0,
      "condition": {
        "type": "value-variable",
        "matchAll": True,
        "assertions": [
          "<StableConditionAssertion>"
        ]
      }
    },
)
data = response.json()

vf message add-variant --message-id <messageID> --project-id <projectID> --environment-alias <environmentAlias> \
  < body.json