List connections a lookup column could read
Every connected integration whose SDK can fetch single records, with the record types it can fetch — the Tools panel’s ‘Your data’ section.
The connection and record-type list costs no network calls (capabilities are read off the SDK class), so a connection with expired credentials still appears, carrying its recorded health. Identity fields DO need the live connection; they are probed best-effort under a short per-connection budget and come back null where the probe failed — the identity-fields endpoint answers live for those.
Authorizations
Bearer authentication header of the form Bearer <token>, where <token> is your auth token.
Response
Successful Response
The connection's last recorded health, or null when never checked.
The system's directory logo; null when the directory has none.
The system behind the connection, e.g. 'clerk'.
The connection's own name, as its owner spelled it.