You can ask Alexa to open Cortana to add tasks from your Amazon Echo to To Do. To start using Microsoft To Do with Alexa:
Make sure that your To Do account is linked to Cortana.
Set up To Do and Cortana with a personal Microsoft account.
Set up the Cortana skill in the Alexa app.
Note: The Cortana skill is still in Preview, so it’s currently only available in US English with personal Microsoft accounts.
Set up To Do and Cortana with a personal Microsoft account:
On PC select Cortana > Notebook > Manage Skills > Manage accounts, or on mobile select Cortana > Settings > Manage accounts.
Select Outlook as your account type.
Connect, and your reminders and lists across Cortana, Microsoft To Do, and Outlook will sync.
Set up the Cortana skill in the Alexa app
Open Alexa and enable Cortana. Select Settings > Skills & Games > Search > then type Cortana.
Sign in to the same Microsoft account that is connected to Microsoft To Do.
Add tasks from Alexa
Say "Alexa, open Cortana" to connect with Cortana and add tasks to Microsoft To Do.
Now try adding a new task to To Do. You can ask her to "add cheese to my Groceries list." Open To Do and you should see that "cheese" has been added to your Groceries list.
See everything you can do with Cortana and Microsoft To Do on TechCommunity.