It’s easy to access many of the Google Cloud Platform APIs from Cloud Function by using a service account to act on your behalf. The service account provides Application Default Credentials for your functions so that you do not need to configure each one to use your personal user credentials.
Cloud Functions can access most major Google Cloud Platform services, including the following:
Supported Event Providers
Currently, Cloud Functions can be triggered by events provided by the following services:
HTTP—invoke functions directly via HTTP requests
Using Services with Cloud Functions
API client libraries that use application default credentials automatically
obtain the built-in service account credentials from the Cloud Functions host at
runtime. By default, the client
<YOUR_PROJECT_ID>@appspot.gserviceaccount.com service account.