diff --git a/NAMESPACE b/NAMESPACE
index 62cbf8f..d03e0c2 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -1,5 +1,6 @@
 # Generated by roxygen2: do not edit by hand
 
+S3method(call_cognitive_endpoint,cognitive_endpoint)
 S3method(print,cognitive_endpoint)
 export(az_cognitive_service)
 export(call_cognitive_endpoint)
diff --git a/R/endpoint.R b/R/endpoint.R
index a8acd07..4d77bbd 100644
--- a/R/endpoint.R
+++ b/R/endpoint.R
@@ -73,6 +73,7 @@ print.cognitive_endpoint <- function(x, ...)
 #' @param http_verb The HTTP verb for the REST call.
 #' @param http_status_handler How to handle a failed REST call. `stop`, `warn` and `message` will call the corresponding `*_for_status` handler in the httr package; `pass` will return the raw response object unchanged. The last one is mostly intended for debugging purposes.
 #' @param auth_header The name of the HTTP request header for authentication. Only used if a subscription key is supplied.
+#' @param ... Further arguments passed to lower-level functions.
 #' @details
 #' This function does the low-level work of constructing a HTTP request and then calling the REST endpoint. It is meant to be used by other packages that provide higher-level views of the service functionality.
 #'
@@ -105,10 +106,18 @@ print.cognitive_endpoint <- function(x, ...)
 #'
 #' }
 #' @export
-call_cognitive_endpoint <- function(endpoint, operation, options=list(), headers=list(), body=NULL, encode=NULL,
-                                    http_verb=c("GET", "POST", "PUT", "PATCH", "DELETE", "HEAD"),
-                                    http_status_handler=c("stop", "warn", "message", "pass"),
-                                    auth_header="ocp-apim-subscription-key")
+call_cognitive_endpoint <- function(endpoint, ...)
+{
+    UseMethod("call_cognitive_endpoint")
+}
+
+#' @rdname call_cognitive_endpoint
+#' @export
+call_cognitive_endpoint.cognitive_endpoint <- function(endpoint, operation,
+    options=list(), headers=list(), body=NULL, encode=NULL, ...,
+    http_verb=c("GET", "POST", "PUT", "PATCH", "DELETE", "HEAD"),
+    http_status_handler=c("stop", "warn", "message", "pass"),
+    auth_header="ocp-apim-subscription-key")
 {
     url <- endpoint$url
     url$path <- file.path(url$path, operation)
diff --git a/man/call_cognitive_endpoint.Rd b/man/call_cognitive_endpoint.Rd
index 2ba1bea..20b2f7f 100644
--- a/man/call_cognitive_endpoint.Rd
+++ b/man/call_cognitive_endpoint.Rd
@@ -2,17 +2,22 @@
 % Please edit documentation in R/endpoint.R
 \name{call_cognitive_endpoint}
 \alias{call_cognitive_endpoint}
+\alias{call_cognitive_endpoint.cognitive_endpoint}
 \title{Call a Cognitive Service REST endpoint}
 \usage{
-call_cognitive_endpoint(endpoint, operation, options = list(),
-  headers = list(), body = NULL, encode = NULL,
-  http_verb = c("GET", "POST", "PUT", "PATCH", "DELETE", "HEAD"),
+call_cognitive_endpoint(endpoint, ...)
+
+\method{call_cognitive_endpoint}{cognitive_endpoint}(endpoint, operation,
+  options = list(), headers = list(), body = NULL, encode = NULL,
+  ..., http_verb = c("GET", "POST", "PUT", "PATCH", "DELETE", "HEAD"),
   http_status_handler = c("stop", "warn", "message", "pass"),
   auth_header = "ocp-apim-subscription-key")
 }
 \arguments{
 \item{endpoint}{An object of class \code{cognitive_endpoint}.}
 
+\item{...}{Further arguments passed to lower-level functions.}
+
 \item{operation}{The operation to perform.}
 
 \item{options}{Any query parameters that the operation takes.}