"He hasn't had the best of series. He would have known that and been disappointed," all-rounder Stokes told Sky Sports.
"From the amount of runs he has got over the last two seasons playing for Durham, and getting 100 in his first England innings, he knows that he can do it."
Lefthander Jennings scored 112 on his test debut in India last December and followed it up with a half-century in the next test against the world's top-ranked side.
But he has failed to show the same level of consistency since, with 48 his highest score in the four-test home series against South Africa.
Jennings will return to Durham and look to recapture the form that earned him selection.
Surrey batsman Stoneman is set to make his debut at Edgbaston and the 30-year-old will become former captain Alastair Cook's 12th opening partner since the retirement of Andrew Strauss in 2012.
England also called up 20-year-old Hampshire leg-spinner Mason Crane for the first time in the longest format after he made his Twenty20 international debut in June.
Paceman Chris Woakes has recovered fully from the side strain he suffered during the Champions Trophy and returned to the squad in place of Steven Finn.
England will host West Indies for two more tests followed by a one-off T20 and a four-match one-day international series.
England squad: Joe Root (captain), Moeen Ali, James Anderson, Jonny Bairstow (wicketkeeper), Stuart Broad, Alastair Cook, Mason Crane, Dawid Malan, Toby Roland-Jones, Ben Stokes, Mark Stoneman, Tom Westley, Chris Woakes
(Writing by Sudipto Ganguly in Mumbai; editing by Ian Ransom)
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