# Overview
## Worker API VIs
There are 4 different types of Worker API VIs that you can create with the Workers API tools. Each API VI and its associated typedefs contain a color glyph on their icons to help identify the purpose of the VI from its icon. Each API VI and associated typedefs also take a filename prefix, to help identify the purpose of the VI from its filename. These API VIs are designed to allow a Worker to communicate only with its Caller, itself, or with a subWorker, and not from any Worker to any other Worker within a Workers application.
{% hint style="info" %}
**Good to know**
All API VIs created in Workers 5.0 are by default **static dispatch** VIs.
{% endhint %}
## MHL Case Sections
The [Public API Builder](/workers-tools/workers-tools-menu/public-api-builder.md) tool and [Create MHL Case](/workers-tools/quickdrop-shortcuts/create-mhl-case-tool-ctrl+9.md) tool will automatically create the MHL cases required to receive the messages sent by the API VIs. These MHL cases will be added to one of three case structure sections (which are also created by the API tools).
* **Local API Cases**
These cases are created by the Create MHL Case tool to receive Local Request messages.
* **Public API Cases**
These cases are created by the Public API Builder tool to receive Public Request messages and Public Request with Reply messages.
* **Response Cases**
These cases are created by the Create MHL Case tool when you create a MHL case with the option 'Add to Response Cases section' selected.
Three MHL case structure sections created and managed by the API tools
## Worker API VI folders
The API VIs will be added to the following folders. VIs that are expected to be used locally (i.e. only by the Worker that owns the VI or by the Worker base class that owns the VI) are set to protected scope. All other VIs are set to Public scope.
Worker API VI folder structure
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