The SDK archive contains the Fuchsia Core SDK, which is a small set of Fuchsia-specific libraries and tools required to start building and running programs for Fuchsia.
This SDK differs from traditional SDKs in that it is not readily usable out of the box. For example, it does not contain any build system, favor any toolchain, or provide standard non-Fuchsia libraries such as for crypto or graphics. Instead, it provides metadata accurately describing its various parts, so that this SDK can be post-processed and augmented with all the pieces necessary for a satisfactory end-to-end development experience.
Most developers who wish to build something for Fuchsia should not need to deal directly with this particular SDK. They will instead consume a transformed version of it, for instance within the development environment and ecosystem supporting a given language runtime. Maintainers of development environments who wish to add support for Fuchsia are the main audience for this SDK. See Integrating the Core SDK for a description of how to process this SDK.
As such, the Core SDK is the representation of the Fuchsia platform developers' contract with other developers who work with Fuchsia. While that contract is absolutely necessary, as this SDK contains the very bits that are unique to Fuchsia, it is not sufficient and will be complemented by other “contracts”. The Fuchsia Core SDK is mirroring the Fuchsia platform in that respect: highly composable and extensible, with a clear separation of concerns.
From this point on, the root of the SDK archive will be referred to as //.
Metadata is present throughout this SDK in the form of JSON files. Every element in this SDK has its own metadata file: for example, a FIDL library //fidl/fuchsia.foobar has its metadata encoded in //fidl/fuchsia.foobar/meta.json.
Every metadata file follows a JSON schema available under //meta/schemas: for example, a FIDL library's metadata file conforms to //meta/schemas/fidl_library.json. Schemas act as the documentation for the metadata and may be used to facilitate the SDK ingestion process. See understanding metadata.
General documentation is available under //docs in the SDK distribution, or online at fuchsia.dev/fuchsia-src/docs/development/sdk. Some individual SDK elements will also provide documentation directly under the path where they are hosted in the SDK.
Target prebuilts are hosted under //arch/<architecture>. This includes a full-fledged sysroot for each available architecture.
The SDK contains sources for a large number of FIDL libraries (under //fidl) as well as a few C/C++ libraries (under //pkg). See compiling C/C++ for details.
Multiple host-side tools can be found under //tools. This includes tools for building programs, deploying to a device, debugging, etc... Some information about how to use these tools can be found under //docs. Specifically:
//device contains metadata describing device configurations matching a given version of the SDK. This metadata contains pointers to images that can be paved onto said devices. See working with devices for how to interact with a device running Fuchsia.
