Why do I only get 20 results from an Availability query?

By default we only return 20 slots or periods from an Availability query. You can change this by using the max_results parameter.

The aim of defaults like this is to provide a high performance, out of the box experience. For the majority of use cases we see, 20 results is a good balance of getting something back to the user as quickly as possible and giving them enough choice. However, you can choose to request more if your use case requires it.

More information in the Availability API reference.