What are my chances of overcoming a "merely descriptive" trademark refusal?

It depends on the strength of the mark and the evidence available. Merely descriptive refusals are among the harder substantive office actions to overcome, but many are successfully resolved.

Arguing suggestiveness is the stronger path where the mark genuinely requires inference to connect to the goods. It does not require evidence gathering and can often be argued purely on the language of the mark. If the argument is persuasive, no further steps are needed.

Acquired distinctiveness is harder to prove, but tends to succeed if the mark has been in long and exclusive use. The USPTO allows a presumption of acquired distinctiveness after five years of exclusive and continuous use, though additional supporting evidence is typically expected alongside it.

Amending to the Supplemental Register is the fallback where neither argument is strong but the mark has some commercial presence. It preserves the application and gives the mark time to build toward Principal Register eligibility.