What are your starting requirements? 2RB, 2WR, and 1 Flex? Is Watson the other guy's only QB?
It's not an automatic accept, even though it looks like a great deal in a vacuum. If you do this trade:
1 - Assuming it's start 1 QB, you're not going to use Watson, so even though I like him better ROS than Carr, it's an upgrade that does you no good behind Brady.
2 - You're going to have to drop Kupp to hold Murray and Henry; can you afford to only roster 3 WRs?
3 - You're going to have to drop someone else to pick up a TE for Gronk's bye in Week 9 (only 2 weeks away) - who do you drop then? Miller? Watson?
Looks like the guy is trying to consolidate a two headed RB into a single one to free up a roster spot, and Jones is the target of the trade for him. But he's partially disguising it as "He's giving you Watson, the hottest QB in the league" as a bonus. However, it's a useless bonus for you (assuming Brady stays healthy of course).
I would do it, only because Murray should be > Jones once he retakes the true lead role if he heals, and if he went down then Henry > Jones as well. Defenses are about to start stacking the box on Jones and making Hundley prove himself. But be prepared to drop someone you don't want to in order to cover Gronk. Including the QBs in the deal just strikes me as useless, but like I said I prefer Watson to Carr so extra bonus for you if Brady does get hurt
Edit to add: If you're not ok with dropping Miller or Watson in a couple weeks, then stand pat and ride Jones while you can