diff --git a/README.md b/README.md
index d68749d..ae2a608 100644
--- a/README.md
+++ b/README.md
@@ -6,14 +6,16 @@ SAKURA Cloud VNC Opener for MacOS
 
 Download a binary from [here](https://github.com/blp1526/scv/releases).
 
-## Usage
-
+## Precondition
 
-1. Create a config file at `$HOME/scv.json`.
+If you use this cli tool, you have to turn on a SAKURA Cloud server power.
 
-1. Write a config file refering to [`scv.sample.json`](scv.sample.json).
+## Usage
 
-1. Run below command.
+* Create a config file at `$HOME/scv.json`.
+* Write a config file refering to [`scv.sample.json`](scv.sample.json).
+  * This file's server name don't have to match the SAKURA cloud sever name.
+* Run below command.
 
 ```
 # format
diff --git a/api/api.go b/api/api.go
index 708017b..e28bb89 100644
--- a/api/api.go
+++ b/api/api.go
@@ -19,7 +19,7 @@ type Body struct {
 	Port     string `json:"Port"`
 }
 
-func Request(body interface{}, zoneName string, serverName string) error {
+func Request(body *Body, zoneName string, serverName string) error {
 	scv := &config.Scv{}
 	current, _ := user.Current()
 	dir := filepath.Join(current.HomeDir, "scv.json")
diff --git a/cmd/cmd.go b/cmd/cmd.go
index 169198d..5559d0f 100644
--- a/cmd/cmd.go
+++ b/cmd/cmd.go
@@ -15,12 +15,12 @@ func Run(zoneName string, serverName string) error {
 		return err
 	}
 
-	vncPath := vncPath(*body)
+	vncPath := vncPath(body)
 	logger.Debug(fmt.Sprintf("VNC Path: %s", vncPath))
 	err = exec.Command("open", vncPath).Run()
 	return err
 }
 
-func vncPath(body api.Body) string {
+func vncPath(body *api.Body) string {
 	return "vnc://:" + body.Password + "@" + body.Host + ":" + body.Port
 }