diff --git a/index.bs b/index.bs
index 759825bf..7eaef595 100644
--- a/index.bs
+++ b/index.bs
@@ -1390,6 +1390,8 @@ Build a composed graph up to a given output operand into a computational graph a
     1. Return |promise|.
 </details>
 
+NOTE: Specifying an [=computational graph/input=] operand or [=computational graph/constant=] operand as a graph {{MLGraphBuilder/build(outputs)/outputs|output}} results in an error, as this is usually an incorrect usage of the API. Callers can work around this by introducing an {{MLGraphBuilder/identity()}} operator.
+
 ### argMin/argMax operations ### {#api-mlgraphbuilder-argminmax}
 Return the index location of the minimum or maxmium values of all the input values along the axes.