アクションの提案は、Google メッセージでのメッセージ リマインダーであり、返信が便利になる機能です。
Nudges gives you 2 types of alerts:
- Reply reminders to follow up after a certain time to a message you sent or received
- Birthday reminders to wish a contact a Happy Birthday
To use Nudges, you must have:
- The Messages app locale set to English (United States).
- An Android OS version L and up. Nudges doesn’t work on Android Go OS devices.
Tip: By default, Nudges is on. To turn off Nudges, at the top right, tap your profile photo 
Learn more about Reply reminders
Reply reminders:
- Prompt you to reply to messages you haven’t yet replied to
- Show outgoing messages that you haven’t followed up on
Google uses Machine Learning models to predict when you send or receive a message that might need follow-up.
A Nudge:
- Shows at the top of your conversation list and in the conversation
- Is dismissed when a new message is sent or received in that conversation
Learn more about Birthday reminders
Birthday reminders:
- Alert you when it’s a saved contact’s birthday
- Prompt you to send a contact a Happy Birthday message
Google:
- Only alerts you if the people you chat with have their birthdays listed in your contacts app
- Moves the conversation to the top of the conversation list
- Adds a message at the top of your conversation that says “It’s their birthday!” and shows a birthday cake icon
- Processes on-device only and birthdays are not uploaded to Google servers