MuleSoft has a proxy service set-up which provides the resources available from a public API.
We have an internal application which, out of the box, can be configured to call and consume resources directly from a traditional API.
The question is if this internal application can hit a standard API should it be able to hit a MuleSoft proxy in the same way, by making a call to an endpoint/method?
Or would we likely need some other/additional kind of client or other configuration to allow this internal application to connect and pull the resources from the MuleSoft proxy service?
Assuming that you are talking about a reasonable standard REST API, that can be defined through a RAML or OAS specification, it should be the same as making requests to the actual API implementation.