diff --git a/cmd/root.go b/cmd/root.go
index e33d457..6030f83 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -8,6 +8,7 @@ import (
 )
 
 var (
+	// DB is database that used by this cli
 	DB database.Database
 
 	rootCmd = &cobra.Command{
diff --git a/database/database.go b/database/database.go
index 0c3edf6..2f52df6 100644
--- a/database/database.go
+++ b/database/database.go
@@ -5,11 +5,21 @@ import (
 	"github.com/RadhiFadlillah/shiori/model"
 )
 
+// Database is interface for manipulating data in database.
 type Database interface {
+	// SaveBookmark saves new bookmark to database.
 	SaveBookmark(bookmark model.Bookmark) (int64, error)
+
+	// GetBookmarks fetch list of bookmarks based on submitted indices.
 	GetBookmarks(withContent bool, indices ...string) ([]model.Bookmark, error)
+
+	// DeleteBookmarks removes all record with matching indices from database.
 	DeleteBookmarks(indices ...string) ([]int, []int, error)
+
+	// SearchBookmarks search bookmarks by the keyword or tags.
 	SearchBookmarks(keyword string, tags ...string) ([]model.Bookmark, error)
+
+	// UpdateBookmarks updates the saved bookmark in database.
 	UpdateBookmarks(bookmarks []model.Bookmark) error
 }
 
diff --git a/database/sqlite.go b/database/sqlite.go
index bb6a0db..0014d92 100644
--- a/database/sqlite.go
+++ b/database/sqlite.go
@@ -10,10 +10,12 @@ import (
 	"strings"
 )
 
+// SQLiteDatabase is implementation of Database interface for connecting to SQLite3 database.
 type SQLiteDatabase struct {
 	sqlx.DB
 }
 
+// OpenSQLiteDatabase creates and open connection to new SQLite3 database.
 func OpenSQLiteDatabase() (*SQLiteDatabase, error) {
 	// Open database and start transaction
 	var err error
@@ -73,6 +75,7 @@ func OpenSQLiteDatabase() (*SQLiteDatabase, error) {
 	return &SQLiteDatabase{*db}, err
 }
 
+// SaveBookmark saves new bookmark to database. Returns new ID and error if any happened.
 func (db *SQLiteDatabase) SaveBookmark(bookmark model.Bookmark) (bookmarkID int64, err error) {
 	// Check URL and title
 	if bookmark.URL == "" {
@@ -156,6 +159,7 @@ func (db *SQLiteDatabase) SaveBookmark(bookmark model.Bookmark) (bookmarkID int6
 	return bookmarkID, err
 }
 
+// GetBookmarks fetch list of bookmarks based on submitted indices.
 func (db *SQLiteDatabase) GetBookmarks(withContent bool, indices ...string) ([]model.Bookmark, error) {
 	// Convert list of index to int
 	listIndex := []int{}
@@ -248,6 +252,7 @@ func (db *SQLiteDatabase) GetBookmarks(withContent bool, indices ...string) ([]m
 	return bookmarks, nil
 }
 
+// DeleteBookmarks removes all record with matching indices from database.
 func (db *SQLiteDatabase) DeleteBookmarks(indices ...string) (oldIndices, newIndices []int, err error) {
 	// Convert list of index to int
 	listIndex := []int{}
@@ -375,6 +380,7 @@ func (db *SQLiteDatabase) DeleteBookmarks(indices ...string) (oldIndices, newInd
 	return oldIndices, newIndices, err
 }
 
+// SearchBookmarks search bookmarks by the keyword or tags.
 func (db *SQLiteDatabase) SearchBookmarks(keyword string, tags ...string) ([]model.Bookmark, error) {
 	// Create initial variable
 	keyword = strings.TrimSpace(keyword)
@@ -440,6 +446,7 @@ func (db *SQLiteDatabase) SearchBookmarks(keyword string, tags ...string) ([]mod
 	return bookmarks, nil
 }
 
+// UpdateBookmarks updates the saved bookmark in database.
 func (db *SQLiteDatabase) UpdateBookmarks(bookmarks []model.Bookmark) (err error) {
 	// Prepare transaction
 	tx, err := db.Beginx()
diff --git a/model/model.go b/model/model.go
index d25951c..4982558 100644
--- a/model/model.go
+++ b/model/model.go
@@ -1,11 +1,13 @@
 package model
 
+// Tag is tag for the bookmark
 type Tag struct {
 	ID      int64  `db:"id"   json:"id"`
 	Name    string `db:"name" json:"name"`
 	Deleted bool   `json:"-"`
 }
 
+// Bookmark is record of a specified URL
 type Bookmark struct {
 	ID          int64  `db:"id"            json:"id"`
 	URL         string `db:"url"           json:"url"`