diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index 0b4a3a6..a840c18 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -258,13 +258,16 @@
 
 /** \def MBEDTLS_CHECK_RETURN
  *
- * This macro appearing at the beginning of the declaration of a function
- * indicates that its return value should be checked.
+ * This macro is used at the beginning of the declaration of a function
+ * to indicate that its return value should be checked. It should
+ * instruct the compiler to emit a warning or an error if the function
+ * is called without checking its return value.
  *
- * Default implementation resides in platform_util.h.
- * You can override default implementation by defining your own.
- * Custom implementation can be empty, which will disable checking
- * of functions' return values.
+ * There is a default implementation for popular compilers in platform_util.h.
+ * You can override the default implementation by defining your own here.
+ *
+ * If the implementation here is empty, this will effectively disable the
+ * checking of functions' return values.
  */
 //#define MBEDTLS_CHECK_RETURN
 
diff --git a/include/mbedtls/platform_util.h b/include/mbedtls/platform_util.h
index 9c64cfd..3a28dac 100644
--- a/include/mbedtls/platform_util.h
+++ b/include/mbedtls/platform_util.h
@@ -60,14 +60,12 @@
 #endif /* MBEDTLS_DEPRECATED_WARNING */
 #endif /* MBEDTLS_DEPRECATED_REMOVED */
 
-/** \def MBEDTLS_CHECK_RETURN
+/* Implementation of the check-return facility.
+ * See the user documentation in mbedtls_config.h.
  *
- * This macro appearing at the beginning of the declaration of a function
- * indicates that its return value should be checked.
- *
- * This should appear before most functions returning an error code
- * (as \c int in the \c mbedtls_xxx API or
- * as ::psa_status_t in the \c psa_xxx API).
+ * Do not use this macro directly to annotate function: instead,
+ * use one of MBEDTLS_CHECK_RETURN_CRITICAL or MBEDTLS_CHECK_RETURN_TYPICAL
+ * depending on how important it is to check the return value.
  */
 #if !defined(MBEDTLS_CHECK_RETURN)
 #if defined(__GNUC__)
@@ -80,6 +78,52 @@
 #endif
 #endif
 
+/** Critical-failure function
+ *
+ * This macro appearing at the beginning of the declaration of a function
+ * indicates that its return value should be checked in all applications.
+ * Omitting the check is very likely to indicate a bug in the application
+ * and will result in a compile-time warning if #MBEDTLS_CHECK_RETURN
+ * is implemented for the compiler in use.
+ *
+ * \note  The use of this macro is a work in progress.
+ *        This macro may be added to more functions in the future.
+ *        Such an extension is not considered an API break, provided that
+ *        there are near-unavoidable circumstances under which the function
+ *        can fail. For example, signature/MAC/AEAD verification functions,
+ *        and functions that require a random generator, are considered
+ *        return-check-critical.
+ */
+#define MBEDTLS_CHECK_RETURN_CRITICAL MBEDTLS_CHECK_RETURN
+
+/** Ordinary-failure function
+ *
+ * This macro appearing at the beginning of the declaration of a function
+ * indicates that its return value should be generally be checked in portable
+ * applications. Omitting the check will result in a compile-time warning if
+ * #MBEDTLS_CHECK_RETURN is implemented for the compiler in use.
+ *
+ * \note  The use of this macro is a work in progress.
+ *        This macro will be added to more functions in the future.
+ *        Eventually this should appear before most functions returning
+ *        an error code (as \c int in the \c mbedtls_xxx API or
+ *        as ::psa_status_t in the \c psa_xxx API).
+ */
+#define MBEDTLS_CHECK_RETURN_TYPICAL MBEDTLS_CHECK_RETURN
+
+/** Benign-failure function
+ *
+ * This macro appearing at the beginning of the declaration of a function
+ * indicates that it is rarely useful to check its return value.
+ *
+ * This macro has an empty expansion. It exists for documentation purposes:
+ * a #MBEDTLS_CHECK_RETURN_OPTIONAL annotation indicates that the function
+ * has been analyzed for return-check usefuless, whereas the lack of
+ * an annotation indicates that the function has not been analyzed and its
+ * return-check usefulness is unknown.
+ */
+#define MBEDTLS_CHECK_RETURN_OPTIONAL
+
 /**
  * \brief       Securely zeroize a buffer
  *