GCP has a GUI for finding and activating APIs called the Cloud API Library. There are three requirements and a sometimes condition for using a Cloud API. The first requirement, pretty obviously, is a Google account. The others seemed a bit more nuanced to me.
The second requirement is a project from which to use the API. In a cloud environment a lot of different software solutions are sharing hardware. Uniquely identified projects enable GCP to isolate what code uses what resources at a given point in time. Having spent some time learning about APIs, I understand that GCP tracks APIs, as part of the software running in the cloud, using their associated projects.
The third requirement involves enabling a particular API for a project. There isn’t one Cloud API; there are many different APIs. APIs exist for software tools like languages (Python, Java, etc), databases, auditing systems and so on. Because most projects only need a fraction of the Cloud APIs available, GCP disables APIs by default. A project must enable an API to use it. In another post, I noted that projects can be created using an API. This isn’t actually the Catch-22 it seems. Software, using certain APIs, can sometimes create or spawn other software. This is something best explored at another time.
And, finally, the sometimes condition mentioned above relates to the fact that some Cloud APIs incur charges in GCP. The next section of the guide deals more specifically with how GCP charges for its resources. At this point, just remember that if an API incurs charges, the project using the API must have an associated billing account in GCP.