---
title: API
---

The REST API client is exposed in the Kernel when packaged as a Docker container, hidden behind a feature flag
that is default set to true. Its main use case is for the Workbench to work.

In addition to this, the Workbench can also be embedded into a client project, it will also then embed the API.

## Internal constructors

When we package assemblies using runtime-only strategy, we perform an [internalization](/chronicle/contributing/clients/internalization/) of types from assemblies
that should not be exposed at compile-time. Some of these types, such as gRPC service contracts are typically things we would like to use
as dependencies on constructors of the controllers.

The problem with this is that we can't have public constructors with dependencies to these types that are runtime-only.

To make this work, the constructors are internal as a consequence.

## Custom Controller Activation

The default activation of controllers is not capable of resolving controllers with internal constructors.
In the `API` client project you'll therefore find a type called `CustomControllerActivator` that is capable of
resolving these.