Endpoints
The Hyfin APIs are standard REST-style APIs that accepts and returns JSON requests and is located at the following endpoints. These endpoint URLs are also referred to as the {base_url} throughout the API documentation.
During your development/integration effort, you should always connect to the STAGE environment. Once you've completed the integration and are ready to go live, you can switch to the PRODUCTION environment by simply changing the URL to point to the production endpoint. You will also need to use your production api_access_token in the request headers.
Both environments also require the integrations.hyfin_api_access feature to be enabled on the site you are calling, in addition to a valid token. The Authentication page describes this prerequisite and quotes the exact error a site without the feature receives.