Lineで利用できる変数です。
Lineのリファレンス Messaging Object を適宜参照してください。
また、管理画面には LINE説明用テンプレート テンプレートがあるので、そちらも参考にして下さい。

共通の変数と、送信したいメッセージ（text, image, imagemap, buttons, confirm, carousel）ごとの変数を以下で説明します。
メッセージでは5個までが一度に送信可能です。

Common variables

Name	Type	Required	Description
app_name	String	○	`line`
lineVersion	String	○	`v2`

Text Message

Name	Type	Required	Description
text	String	○	Text Max: 2000 characters

🚧
テキスト内URLのクリック計測
現状テキスト内のURLはクリックの計測はされません。自動的な短縮化も行いません。

Name	Type	Required	Description
image	String	○	Image URL Max: 1000 characters HTTPS JPEG Max: 1024 x 1024 Max: 1 MB

Name	Type	Required	Description
imagemap	Object (Folder)	○
imagemap.altText	String	○	Alternative text Max: 400 characters
imagemap.baseUrl	String	○	Base URL of the image Max: 1000 characters HTTPS
imagemap.baseSize	Object (Folder)	○
imagemap.baseSize.width	Number	○	Width of base image in pixels. Set to 1040.
imagemap.baseSize.height	Number	○	Height of base image. Set to the height that corresponds to a width of 1040 pixels.
imagemap.actions[]	Array (List)	○	Action when tapped Max: 50
imagemap.actions[].type	String	○	`uri`
imagemap.actions[].linkUri	String	○	Webpage URL Max: 1000 characters Automatically convert this field into `https://s.karte.io/xxx` formats for click tracking.
imagemap.actions[].area	Object (Folder)	○	Defined tappable area
imagemap.actions[].area.x	Number	○	Horizontal position relative to the top-left corner of the area
imagemap.actions[].area.y	Number	○	Vertical position relative to the top-left corner of the area
imagemap.actions[].area.width	Number	○	Width of the tappable area
imagemap.actions[].area.height	Number	○	Height of the tappable area

Name	Type	Required	Description
buttons	Object (Folder)	○
buttons.altText	String	○	Alternative text. Max: 400 characters
buttons.title	String		Title Max: 40 characters
buttons.text	String	○	Message text Max: 160 characters (no image or title) Max: 60 characters (message with an image or title)
buttons.thumbnailImageUrl	String		Image URL (Max: 1000 characters) HTTPS JPEG or PNG Max width: 1024px Max: 1 MB
buttons.actions[]	Array (List)	○	Action when tapped Max: 4 See Action Object

Name	Type	Required	Description
confirm	Object (Folder)	○
confirm.altText	String	○	Alternative text. Max: 400 characters
confirm.text	String	○	Message text Max: 240 characters
confirm.actions[]	Array (List)	○	Action when tapped Set 2 actions for the 2 buttons See Action Object

Name	Type	Required	Description
carousel	Object (Folder)	○
carousel.altText	String	○	Alternative text. Max: 400 characters
carousel.columns[]	Array (List)	○	Array of columns Max: 10
carousel.columns[].thumbnailImageUrl	String		Image URL (Max: 1000 characters) HTTPS JPEG or PNG Max width: 1024px Max: 1 MB
carousel.columns[].title	String		Title Max: 40 characters
carousel.columns[].text	String	○	Message text Max: 120 characters (no image or title) Max: 60 characters (message with an image or title)
carousel.columns[].actions[]	Array (List)	○	Action when tapped Max: 3 See Action Object

Name	Type	Required	Description
type	String	○	`message` or `uri`
label	String	○	Label for the action Required for templates other than image carousel. Max: 20 characters. Optional for image carousel templates. Max: 12 characters. Optional for rich menus. Spoken when the accessibility feature is enabled on the client device. Max: 20 characters. Supported on LINE 8.2.0 and later for iOS. Required for quick reply buttons. Max: 20 characters. Supported on LINE 8.11.0 and later for iOS and Android. Requird for the button component of Flex Message. This property can be specified for the box, image, and text components but its value is not displayed. Max: 20 characters.
text	String	○ (if type is `message`)	Text sent when the action is performed Max: 300 characters
uri	String	○ (if type is `uri`)	URI opened when the action is performed (Max: 1000 characters) The available schemes are http, https, line, and tel. Automatically convert this field into `https://s.karte.io/xxx` formats for click tracking.