diff --git a/docs/src/interfaces.md b/docs/src/interfaces.md
index 591e7b4..9651ec6 100644
--- a/docs/src/interfaces.md
+++ b/docs/src/interfaces.md
@@ -39,6 +39,7 @@ Supposition.target!(::Float64)
 Supposition.assume!(::Bool)
 Supposition.produce!(::Data.Possibility)
 Supposition.reject!
+Supposition.err_less
 Supposition.DEFAULT_CONFIG
 ```