Dialogflow uses Google for authentication, which requires a few permissions. This page explains these permissions and what they're related to.
When you log in to Dialogflow for the first time, you'll see the following permissions needed in order to use Dialogflow:
View and manage your data across Google Cloud Platform services
This permission is to deploy Cloud Functions for Firebase on your behalf to (optionally) power your Dialogflow agent. See Fulfillment for more information.
View and manage your Google Assistant voice commands, dialog and grammar
This permission is to allow you to test your Dialogflow agent on the Google Assistant. See Google Assistant integration for more information.
View and manage your Actions on Google
This permission is to allow you to deploy your Dialogflow agent to the Google Assistant and Actions on Google as a conversational action(s).