The phrase "tricky to assess" is a correct and usable phrase in written English.
You can use it to describe a situation that is difficult to evaluate or measure, like a complicated problem or an open-ended question. For example: "The question of whether a ban on plastic bags would reduce littering is tricky to assess, given that there are so many different variables to consider."
Hamstring injuries can be tricky to assess.
Ms. Trump's negotiating prowess is tricky to assess, as no reporter has sat at her elbow in a business meeting.
But research in this area is not very scientific because the role of relative attractiveness is tricky to assess when so many other factors matter in relationships.
Bankers said details of the debt swap and other features of the rescue package remained foggy, and therefore it was tricky to assess the true impact.
Polar bears, which hunt for seals along the ice's edge, and walruses, which fish there, will both be hard-hit.The effects on the wider climate are tricky to assess.
Only time will tell whether such a long fix at this rate represents great value, but even the experts and economists don't know with any certainty when rates will rise and this has made long-term fixes tricky to assess.
It is much trickier to assess Leibniz's contribution to his research environment, as there wasn't really a research environment that he could contribute to.
How they used that extra brain power is a little trickier to assess, though most scientists believe it maintained complex, extended social networks.
The black-carbon measures save a lot more lives than ozone control, but are trickier to assess in terms of climate.Clearing the airUNEP's interest in black carbon dates back to a plane journey taken a decade ago.
It's certainly a tricky one to assess.
Weblogs ("blogs") offer a deeply rewarding online experience because they provide a rich mix of expert opinion and instruction, diary-like personal narrative, journalism, and online community; but for just these reasons, they can be particularly tricky to understand, assess, and discover.
