OAuth Web Service for the Docusign REST API (Docusign also produces an OpenAPI Specification that can easily be imported into the HTTPCaller Transformer). Please note:

For the developer environment, the URI is

https://account-d.docusign.com/oauth/token

For the production environment, the URI is

https://account.docusign.com/oauth/token

For more details, please refer to step 2. Obtain the access token documentation.