It sounds like you're referring to the
Bulk Uploader utility, which is typically used to upload IDs to user lists in large quantities. If you're not familiar with that though, there is some preparatory work needed to work with those IDs–i.e. they need to be matched via
Cookie Matching in order to be uploaded to a user list. We don't have code examples for this particular utility, but we at least have
examples for what a typical payload might look like in the request, and how the response would appear in practice. Keep in mind though that these are human-readable representations of data sent as serialized
Protobuf messages–you'll need to compile
cookie-bulk-upload-proto.txt to get a library used to serialize / deserialize these messages.