API Designer

API Designer provides a web-based interface for designing, documenting, testing, and sharing API specifications and fragments.


You can use either the text editor or the visual editor to create API specifications in RESTful API Modeling Language (RAML) version 0.8 or 1.0, or according to OpenAPI specification (OAS) version 2.0 or 3.0.

With the text editor, you can:

  • Design according to best practices with a context-aware shelf that auto-populates with the appropriate methods, resources, parameters, and security components.

  • Include RAML API fragments, such as security schemas and data types, from Exchange or write your own.

  • Import existing API specifications.

With the visual editor, you can:

  • Create a specification for use cases in which you do not need to include RAML fragments.

  • Scaffold a specification that you can complete and customize in the text editor.


As you add descriptions in your specifications and fragments, you can view them in auto-generated, interactive documentation in the right-hand pane of the text editor.


You can use the mocking service to:

  • Preview an API’s functionality before writing a single line of code.

  • Send requests to the specification and receive defined responses.

  • Use behavioral headers to simulate different scenarios, such as timeouts and errors.


You can publish an API specification to Anypoint Exchange for use in API Manager, Anypoint Studio, or Flow Designer. You can also add an API specification directly to API Manager.

How API Designer Relates to Other MuleSoft Products

API Designer is an integral part of the MuleSoft API-led approach to integrating applications. The following diagram depicts how the API specifications that you write in API Designer can be used in other MuleSoft products.

apid system overview

A specification writer uses API Designer to design API specifications and RAML fragments. RAML specifications can use assets that are hosted in Exchange. The specification writer can publish iterations and final versions to Anypoint Exchange.

From Exchange, the specification can be imported into Anypoint Studio and Flow Designer as a RESTful connector, or into API Manager. Anypoint Studio can even import a specification directly from API Designer.

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