word choice - Correct use of "proof-of-concept"

In writing a technical paper, I'm wondering about the correct use of proof-of-concept.

In short, the situation is that we have developed an application/tool to show the feasibility of a new approach to a problem, i.e. a proof-of-concept.

Now in the paper itself, which of the following would be better to use?

• Therefore, the proof-of-concept tool proposed in this paper...


• Therefore, the proof-of-concept proposed in this paper...

I'm not sure how to formally say this in English, but I guess the question is: can proof-of-concept be used to refer to the thing itself, or is it used as an adjective?

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