diff --git a/interfaces.go b/interfaces.go
new file mode 100644
index 0000000..671fa1a
--- /dev/null
+++ b/interfaces.go
@@ -0,0 +1,17 @@
+package gophercloud
+
+// AccessProvider instances encapsulate a Keystone authentication interface.
+type AccessProvider interface {
+	// FirstEndpointUrlByCriteria searches through the service catalog for the first
+	// matching entry endpoint fulfilling the provided criteria.  If nothing found,
+	// return "".  Otherwise, return either the public or internal URL for the
+	// endpoint, depending on both its existence and the setting of the ApiCriteria.UrlChoice
+	// field.
+	FirstEndpointUrlByCriteria(ApiCriteria) string
+}
+
+// ComputeProvider instances encapsulate a Cloud Servers API, should one exist in the service catalog
+// for your provider.
+type ComputeProvider interface {
+	ListServers() ([]Server, error)
+}