"the only caution" is a perfectly acceptable and usable phrase in written English.
You can use it when something is the only thing to be careful of or to be warned about. For example: "The only caution when starting a new business is to make sure you have proper funding."
The only caution in cooking with miso is that it must be handled gently; high heat practically destroys its flavor.
The only caution is that a high-calorie diet is often synonymous with a high-fat, high-cholesterol and high-sugar regimen that might introduce health problems more serious than the few pounds the person may be missing.
The only caution I'd issue is to avoid anything too delicate, because it will inevitably be buried by the deluge of flavours – I like Isle of Arran, Chivas Regal, Singleton, Macallan and Glenlivet, but all of them are lost here.
The only caution that should be offered to the present is that Attlee's government was to a significant extent consumed by foreign and defence issues, and took its eye off the domestic ball.
The only caution for ANS is a possible fracture of whole ANS which can cause nasal tip deformity.
The only caution is that, before the algo is promoted, the company needs to be sure what it is asking for.
The only cautions I might offer about the author's points would be the growing evidence base against the notion that whole grains are healthy, and the evidence that labeling polyphenols as 'antioxidants' is misleading.
In each of her two previous matches, Lambert had received a yellow-card warning, but those were the only cautions in more than 2,500 minutes of play at New Mexico, a university official said.
The only caveat, Greenberg cautioned, is that it's typically harder for a student to get big-time financial aid when not applying as a freshman.
Jarrett's Pontiac slammed into the fourth-turn wall, bringing out the race's only caution.
But I did not divulge the content of the letter, only cautioned my student.
