diff --git a/crates/jsonschema-cli/README.md b/crates/jsonschema-cli/README.md
index 9ea62ba0..5d4051aa 100644
--- a/crates/jsonschema-cli/README.md
+++ b/crates/jsonschema-cli/README.md
@@ -14,6 +14,8 @@ cargo install jsonschema-cli
 jsonschema [OPTIONS] <SCHEMA>
 ```
 
+**NOTE**: It only supports valid JSON as input.
+
 ### Options:
 
 - `-i, --instance <FILE>`: JSON instance(s) to validate (can be used multiple times)