Define API

Describe the operations of your API in one of the supported API definition languages:


API definitions can be converted between formats by doing one of the following:

  • Use the Facility Editor. Enter an FSD or Swagger API definition in the left pane, choose the “Swagger” or “FSD” generator, and copy the generated definition from the right pane (or click Download).
  • Run the fsdgenfsd tool (see below) on the command line or in a build script.
  • Use the Facility.Definition .NET library (NuGet Package) in your own build tool.


fsdgenfsd is a command-line tool that can convert a service definition between the supported API definition languages. It can also be used to “normalize” an API definition by “converting” it to the same format.

Install fsdgenfsd as documented from its NuGet package.

fsdgenfsd generates a single file and supports the standard command-line options as well as the following additional command-line options:

  • --swagger: Generates Swagger (OpenAPI) 2.0. If omitted, the tool generates FSD.
  • --yaml: When used with --swagger, generates YAML instead of JSON.