First version of the README file.

README.md

@@ -1,2 +1,51 @@
-# adyen-openapi
-OpenAPI specification for the Adyen APIs
+# Adyen OpenAPI / Swagger specifications
+
+Adyen provides you with [plenty of different APIs](https://docs.adyen.com/developers) that help you accept payments on your website or mobile application, implement subscription billing, make payouts, and much more.
+
+This repository contains Adyen API specifications, represented in the [OpenAPI standard](https://www.openapis.org/) (former Swagger specification).
+
+## Folder structure
+
+All specifications in this repository are organized into two subfolders:
+
+```
+/specs
+   /2.0 – Spec files in the OpenAPI 2.0 format.
+   /3.0 – Spec files in the OpenAPI 3.0.0 format.
+```
+
+We provide specifications in both `.json` and `.yaml` formats, with an API version number (e.g. `v30`) in a file name.
+
+## Usage
+  
+There are multiple ways you can use the OpenAPI specification to explore the Adyen API:
+-	If you want to see the OpenAPI specification in action, visit the [Adyen API Explorer](https://docs.adyen.com/api-explorer/) portal.
+-	If you prefer to use the classic Swagger toolset, upload these specifications to the [Swagger Editor](http://editor.swagger.io/) or [SwaggerHub](https://swaggerhub.com/).
+-	Also we recommend you use [Postman](https://www.getpostman.com/postman) to import the OpenAPI specification and create your personal collection of requests.
+
+## Custom extensions
+
+Adyen specifications contain a few custom extensions, which are [allowed by the OpenAPI standard](https://swagger.io/docs/specification/openapi-extensions/). These extensions are used to provide metadata about API objects, for instance, to set grouping and sort order when displaying them in the [Adyen API Explorer](https://docs.adyen.com/api-explorer/).
+
+For example:
+
+```
+"x-groups" : [
+   "General",
+   "Modifications"
+],
+
+   "post" : {
+       "x-groupName" : "Modifications",
+       "x-sortIndex" : 5,
+```
+
+  
+## Support
+  
+If you have any questions or suggestions, please feel free to create an issue here or contact [Adyen Support](https://support.adyen.com).
+  
+## License 
+
+This repository is open source and available under the MIT license. For more information, see the LICENSE file.
+