s_level</code> | integer | yes | A valid access level |
| <code>expires_at</code> | string | no | A date string in the format YEAR-MONTH-DAY |
| <code>invite_source</code> | string | no | The source of the invitation that starts the member creation process. See <a href="https://gitlab.com/gitlab-org/gitlab/-/issues/327120">this issue</a>. |
| <code>member_role_id</code> | integer | no | Assigns the new member to the provided custom role. (<a href="https://gitlab.com/gitlab-org/gitlab/-/merge_requests/134100