diff --git a/core/api.go b/core/api.go
index ff10666..8e2950a 100644
--- a/core/api.go
+++ b/core/api.go
@@ -29,14 +29,14 @@ import (
 )
 
 type fileDocumentDesc struct {
-	Service   string
-	Key       string
-	Src       string
-	Link      string
-	Desc      string
-	Extract   bool
-	Timestamp int64
-	Contents  []byte `json:",omitempty"`
+	Service   string `bson:"service" json:"service"`
+	Key       string `bson:"key" json:"key"`
+	Src       string `bson:"src" json:"src"`
+	Link      string `bson:"link" json:"link"`
+	Desc      string `bson:"desc" json:"desc"`
+	Extract   bool   `bson:"extract" json:"extract"`
+	Timestamp int64  `bson:"timestamp" json:"timestamp"`
+	Contents  []byte `bson:"contents,omitempty" json:"contents,omitempty"`
 }
 
 func (fd *fileDocumentDesc) save() error {