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 # Creating add-in applications

 Last update: 09.03.2026 

The Discovery Application Programming Interface (API) Developer Guide contains documentation and samples that allow you to create add-in applications that extend the functionality of Discovery. An add-in is a managed code DLL that uses the Discovery API. The API version referred to in this document is API.V22.

This document contains information on the following:

- The basic infrastructure for add-in customization.
- How to add custom elements to the User Interface.
- An overview of the geometry architecture.

This section contains the following topics:

- **[Getting started](./c_disco_api_addin_gettingstarted.md)**
- **[Creating a C# add-in](./c_disco_api_create_csharp.md)**
- **[Creating manifest files](./c_disco_api_manifest.md)**
- **[Creating custom commands](./c_disco_api_create_custom.md)**
- **[Customizing the ribbon](./c_disco_api_ribbon_customize.md)**
- **[Customizing tools](./c_disco_api_tool_customize.md)**
- **[Custom objects and custom tree](./c_disco_api_custom_objects_custom_tree.md)**
- **[Sample projects](./c_disco_api_samples.md)**