A Software Developer Kit (SDK) is a package of tools to help developers get started with a programming project. An SDK may include how-to instruction guides, documentation, code libraries, frameworks, sample code, or other helpful programming resources. For example, the Android SDK provides the scaffolding necessary to help developers build apps for the Android platform. All SDKs are different, and specific requirements vary according to the project at hand. SDKs are typically downloaded directly from a software provider so that the developer can access the resources they need on their local device. SDKs are common among API providers that offer multiple ways to engage with the platform. For example, an eCommerce Software-as-a-Service may invite third-party developers to build integrations to enhance their marketplace functionality. An SDK for this scenario could house a sample project, an integration walkthrough, a development environment to build an app, and branding guidelines with image files.