ActionParameter: List of string parameters to supply when the action method is invoked.

ActionResponse: Parameters that a bot can use to configure how it's response is posted.

Annotation: Annotations associated with the plain-text body of the message.

Button: A button.

Card: A card is a UI element that can contain UI widgets such as texts, images.

CardAction: A card action is the action associated with the card.

DeprecatedEvent: Hangouts Chat events.

Empty: A generic empty message that you can re-use to avoid defining duplicated empty messages in your APIs.

FormAction: A form action describes the behavior when the form is submitted.

Image: An image that is specified by a URL and can have an onclick action.

ImageButton: An image button with an onclick action.

KeyValue: A UI element contains a key (label) and a value (content).

Membership: Represents a membership relation in Hangouts Chat.

Message: A message in Hangouts Chat.

OnClick: An onclick action (e.g.

OpenLink: A link that opens a new window.

Section: A section contains a collection of widgets that are rendered (vertically) in the order that they are specified.

Space: A room or DM in Hangouts Chat.

TextButton: A button with text and onclick action.

TextParagraph: A paragraph of text.

Thread: A thread in Hangouts Chat.

User: A user in Hangouts Chat.

UserMentionMetadata: Annotation metadata for user mentions (@).

WidgetMarkup: A widget is a UI element that presents texts, images, etc.