Just take a look at some of Jay's outstanding and critically important achievements:
- President of the Continental Congress
- Diplomat (both during the Revolution and during the Washington administration -- the Jay Treaty with Britain is named after him)
- Co-author of The Federalist Papers (with Hamilton and Madison)
- First Chief Justice of the United States Supreme Court
- Governor of New York
- Key mover behind New York's move for the gradual abolition of slavery in the 1790s
And while Jay may legitimately be excluded from the list of the "top tier" Founders, he still had a key role to play in both the success of the Revolution and the life of the early Republic at both the state and federal level. And he was a leader in the early effort to acknowledge the full humanity of African-Americans in our country (something that can't be said about several of the "top tier" Founders like Jefferson and Madison).
He was a key Founder.