Is salvation by grace, through faith, not of works, as the Bible says? If you say yes, you're correct. If you say no, works are involved, it is entirely accurate to say you have a works-based "gospel".
But most merit mongers will not admit this. In fact, if you say their "gospel" is works-based, they may accuse you of, at best, misunderstanding them. At worst, committing the straw man fallacy. After all, they still believe salvation requires faith, and that works are insufficient in and of themselves. But ironically, this, in itself, is a straw man. See, hardly anyone believes we are saved by works alone. Faith alone? Yes, the Bible actually says this. But works alone is an exceptionally rare position among nominal Christians.
Nevertheless, the question isn't whether you believe works are the sole criteria for salvation, but whether you believe it is a criteria at all. Is there anything you can do to earn salvation? Most merit-mongers would say actually, no. You'll get the odd Liberal who would say "sure, just be a good person, God loves everyone, so even an atheist will probably get into Heaven if he's a decent guy". But the very definition of salvation requires our inability to earn it for ourselves.
But is there something you must do to earn salvation? This is where the Bible is pretty clear: "And he brought them out and said, “Sirs, what must I do to be saved?” So they said, “Believe on the Lord Jesus Christ, and you will be saved, you and your household.”" (Acts 16:30-31). This would have been the perfect time for Paul and Silas to mention just about any work any counterfeit faith says is required for salvation, but he doesn't. He just says "believe on the Lord Jesus Christ". So what must you do to be saved? Believe.
It's clear, then, that Biblically, works are not involved in salvation. But do you believe they are? Do you believe, for example, one must be baptised to be saved? Congratulations, you have a works-based "gospel", because works are essential in your gospel. Works = maybe saved, no works = not saved. It's like saying an egg-based cake. Eggs may not be the only ingredient in the cake, but without the eggs, you aren't getting the cake.
So where is the straw man? Where is the misrepresentation? If you believe works are required for salvation, you do have a works-based "gospel". The problem is, such a "gospel" is a fraud. In the Bible, you are not required to do anything for salvation that you couldn't do with your arms and legs nailed to a cross. How do we know? Because one of the men nailed to the cross next to Jesus was saved by faith alone. His one and only "work" was confessing Jesus as Lord, yet the Lord said to him "Assuredly, I say to you, today you will be with Me in Paradise." (Luke 23:43).
If you believe in works as a requirement for earning or maintaining salvation, you believe in a works-based "gospel". That is no straw man. But if you believe in such works-based "gospels", you're building with straw, man! Your works will be burned up by God's Holy fire. Will you be saved through this fire? Truthfully, probably not. Paul says that if anyone preaches a different gospel than his Gospel, let him be accursed (Galatians 1:8). Apostle, angel, heretic, no one has the right to preach a different gospel. Therefore, the real issue isn't how accurate people's summaries of your "gospel" is, but how accurate your "gospel" is. If it doesn't match Paul's, it has no power to save. But no "gospel" involving works matches Paul's.