curl --request POST \
  --url https://sandbox.api.app.firstsales.io/api/v1/organizations/{orgId}/workspaces/{wsId}/inbox/threads/{threadId}/reply \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "connectorId": "<string>",
  "subject": "<string>",
  "body": "<string>"
}
'

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({connectorId: '<string>', subject: '<string>', body: JSON.stringify('<string>')})
};

fetch('https://sandbox.api.app.firstsales.io/api/v1/organizations/{orgId}/workspaces/{wsId}/inbox/threads/{threadId}/reply', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

{}

{
  "error": {
    "code": "<string>",
    "message": "<string>",
    "requestId": "<string>",
    "details": {}
  }
}