diff --git a/grammars/README.md b/grammars/README.md
index daac7f4d8d..dcd28648b1 100644
--- a/grammars/README.md
+++ b/grammars/README.md
@@ -150,6 +150,9 @@ You can use GBNF grammars:
     - in CLI, with [examples/json_schema_to_grammar.py](../examples/json_schema_to_grammar.py)
     - in JavaScript with [json-schema-to-grammar.mjs](../tools/server/public_legacy/json-schema-to-grammar.mjs) (this is used by the [server](../tools/server)'s Web UI)
 
+> [!NOTE]
+> The JSON schema is only used to constrain the model output and is not injected into the prompt. The model has no visibility into the schema, so if you want it to understand the expected structure, describe it explicitly in your prompt. This does not apply to tool calling, where schemas are injected into the prompt.
+
 Take a look at [tests](../tests/test-json-schema-to-grammar.cpp) to see which features are likely supported (you'll also find usage examples in https://github.com/ggml-org/llama.cpp/pull/5978, https://github.com/ggml-org/llama.cpp/pull/6659 & https://github.com/ggml-org/llama.cpp/pull/6555).
 
 ```bash