The enumeratesigners RPC returns a list of external signers from -signer.
enumeratesigners none
*bitcoin-cli help enumeratesigners
enumeratesigners Returns a list of external signers from -signer. Result: { (json object) "signers" : [ (json array) { (json object) "fingerprint" : "hex", (string) Master key fingerprint "name" : "str" (string) Device name }, ... ] } Examples: > bitcoin-cli enumeratesigners > curl --user myusername --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "enumeratesigners", "params": []}' -H 'content-type: text/plain;' http://127.0.0.1:8332/