diff --git a/staging/src/k8s.io/apiserver/pkg/server/options/etcd.go b/staging/src/k8s.io/apiserver/pkg/server/options/etcd.go
index 41075fea247..4d97566e67d 100644
--- a/staging/src/k8s.io/apiserver/pkg/server/options/etcd.go
+++ b/staging/src/k8s.io/apiserver/pkg/server/options/etcd.go
@@ -137,13 +137,18 @@ func (s *EtcdOptions) AddFlags(fs *pflag.FlagSet) {
 	fs.IntVar(&s.DefaultWatchCacheSize, "default-watch-cache-size", s.DefaultWatchCacheSize,
 		"Default watch cache size. If zero, watch cache will be disabled for resources that do not have a default watch size set.")
 
+	fs.MarkDeprecated("default-watch-cache-size",
+		"watch caches are sized automatically and this flag will be removed in a future version")
+
 	fs.StringSliceVar(&s.WatchCacheSizes, "watch-cache-sizes", s.WatchCacheSizes, ""+
 		"Watch cache size settings for some resources (pods, nodes, etc.), comma separated. "+
 		"The individual setting format: resource[.group]#size, where resource is lowercase plural (no version), "+
 		"group is omitted for resources of apiVersion v1 (the legacy core API) and included for others, "+
-		"and size is a number. It takes effect when watch-cache is enabled. "+
-		"Some resources (replicationcontrollers, endpoints, nodes, pods, services, apiservices.apiregistration.k8s.io) "+
-		"have system defaults set by heuristics, others default to default-watch-cache-size")
+		"and size is a number. This option is only meaningful for resources built into the apiserver, "+
+		"not ones defined by CRDs or aggregated from external servers, and is only consulted if the "+
+		"watch-cache is enabled. The only meaningful size setting to supply here is zero, which means to "+
+		"disable watch caching for the associated resource; all non-zero values are equivalent and mean "+
+		"to not disable watch caching for that resource")
 
 	fs.StringVar(&s.StorageConfig.Type, "storage-backend", s.StorageConfig.Type,
 		"The storage backend for persistence. Options: 'etcd3' (default).")