curl \
  <JSON_RPC_URL> \
  -H 'content-type: application/json' \
  --data @- <<'EOF'
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "selfSignedAccessToken",
  "params": {
    "params": {
      "networkId": "<string>",
      "clientId": "<string>",
      "clientSecret": "<string>"
    }
  }
}
EOF