diff --git a/include/mbedtls/x509.h b/include/mbedtls/x509.h
index 8582e76..ef4d75d 100644
--- a/include/mbedtls/x509.h
+++ b/include/mbedtls/x509.h
@@ -473,7 +473,6 @@
                                size_t val_len);
 int mbedtls_x509_write_extensions(unsigned char **p, unsigned char *start,
                                   mbedtls_asn1_named_data *first);
-
 int mbedtls_x509_write_names(unsigned char **p, unsigned char *start,
                              mbedtls_asn1_named_data *first);
 int mbedtls_x509_write_sig(unsigned char **p, unsigned char *start,
diff --git a/include/mbedtls/x509_crt.h b/include/mbedtls/x509_crt.h
index 57e3cce..537408e 100644
--- a/include/mbedtls/x509_crt.h
+++ b/include/mbedtls/x509_crt.h
@@ -241,6 +241,18 @@
 }
 mbedtls_x509write_cert;
 
+/**
+ * \brief           Set Subject Alternative Name
+ *
+ * \param ctx       Certificate context to use
+ * \param san_list  List of SAN values
+ *
+ * \return          0 if successful, or MBEDTLS_ERR_X509_ALLOC_FAILED
+ *
+ * \note            "dnsName", "uniformResourceIdentifier", "IP address",
+ *                  "otherName", and "DirectoryName", as defined in RFC 5280,
+ *                  are supported.
+ */
 int mbedtls_x509write_crt_set_subject_alternative_name(mbedtls_x509write_cert *ctx,
                                                        const mbedtls_x509_san_list *san_list);