Initialize useful errors.
diff --git a/openstack/identity/v3/endpoints/errors.go b/openstack/identity/v3/endpoints/errors.go
new file mode 100644
index 0000000..a8b00d4
--- /dev/null
+++ b/openstack/identity/v3/endpoints/errors.go
@@ -0,0 +1,21 @@
+package endpoints
+
+import "fmt"
+
+func requiredAttribute(attribute string) error {
+	return fmt.Errorf("You must specify %s for this endpoint.", attribute)
+}
+
+var (
+	// ErrInterfaceRequired is reported if an Endpoint is created without an Interface.
+	ErrInterfaceRequired = requiredAttribute("an interface")
+
+	// ErrNameRequired is reported if an Endpoint is created without a Name.
+	ErrNameRequired = requiredAttribute("a name")
+
+	// ErrURLRequired is reported if an Endpoint is created without a URL.
+	ErrURLRequired = requiredAttribute("a URL")
+
+	// ErrServiceIDRequired is reported if an Endpoint is created without a ServiceID.
+	ErrServiceIDRequired = requiredAttribute("a serviceID")
+)