curl --request GET \
  --url https://hub-api.neynar.com/v1/onChainSignersByFid \
  --header 'x-api-key: <api-key>'

{
  "type": "EVENT_TYPE_SIGNER",
  "chainId": 123,
  "blockNumber": 123,
  "blockHash": "0x75fbbb8b2a4ede67ac350e1b0503c6a152c0091bd8e3ef4a6927d58e088eae28",
  "blockTimestamp": 123,
  "transactionHash": "0x36ef79e6c460e6ae251908be13116ff0065960adb1ae032b4cc65a8352f28952",
  "logIndex": 123,
  "txIndex": 123,
  "fid": 123,
  "signerEventBody": {
    "key": "<string>",
    "keyType": 123,
    "eventType": "SIGNER_EVENT_TYPE_ADD",
    "metadata": "aSDinaTvuI8gbWludGxpZnk=",
    "metadataType": 123
  }
}