curl --request POST \
  --url https://tryno.io/api/threads/{threadId}/messages \
  --cookie __session=

const options = {method: 'POST', headers: {cookie: '__session='}};

fetch('https://tryno.io/api/threads/{threadId}/messages', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://tryno.io/api/threads/{threadId}/messages"

headers = {"cookie": "__session="}

response = requests.post(url, headers=headers)

print(response.text)

{}

{
  "error": "<string>"
}

{
  "error": "<string>"
}