diff --git a/include/mbedtls/cipher.h b/include/mbedtls/cipher.h
index 7921f4d..b4630f6 100644
--- a/include/mbedtls/cipher.h
+++ b/include/mbedtls/cipher.h
@@ -258,6 +258,13 @@
 /**
  * Cipher information. Allows calling cipher functions
  * in a generic way.
+ *
+ * \note        The library does not support custom cipher info structures,
+ *              only built-in structures returned by the functions
+ *              mbedtls_cipher_info_from_string(),
+ *              mbedtls_cipher_info_from_type(),
+ *              mbedtls_cipher_info_from_values(),
+ *              mbedtls_cipher_info_from_psa().
  */
 typedef struct mbedtls_cipher_info_t
 {
diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index ded5222..5f9f29f 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -186,6 +186,10 @@
 
 /**
  * \brief           Public key information and operations
+ *
+ * \note        The library does not support custom pk info structures,
+ *              only built-in structures returned by
+ *              mbedtls_cipher_info_from_type().
  */
 typedef struct mbedtls_pk_info_t mbedtls_pk_info_t;