Do we have any validation done for the Username

[Informatica CloudConnectivityDev]

Do we have any validation done for the Username when we connect to jira endpoint?

We wanted to get above information because when we try to make request to jira endpoint we are getting 200 OK as a response even though the username is invalid.
Example :

For API Key we see a validation from jira end, but not for username.

Please let us know if there are any other mechanism to validate the username.