diff --git a/src/main/webapp/doc/api.txt b/src/main/webapp/doc/api.txt
index af3b416..fa46d0a 100644
--- a/src/main/webapp/doc/api.txt
+++ b/src/main/webapp/doc/api.txt
@@ -2,6 +2,7 @@ attach: {
     _id:...
     "ossurl":...
     "filename": ...
+    other optinal key-values...
 }
 upload (json optional, file) {
     return attach json