If my novel has two protagonists, is it OK to include both in the query? Both are equally important and have equally high stakes. The novel is told from both POV's, switching back and forth from chapter to chapter. I've gotten some feedback (not agent) telling me to narrow the query down to one character to keep it simpler, but I've also heard the opposite.
There is no right answer here. There's only what works. The purpose of a query is to entice the reader (in this case an agent) to read more pages. Does your query do this? If it does, it's effective. If it doesn't it's ineffective.
Rules about query letters are to help you avoid the pitfalls that can diminish effectiveness. Rules don't create an effective query; rules help you avoid being ineffective. It's a subtle distinction but it's important.
It's a distinction I hear a lot about over at QueryShark. "Show us what works!" queriers write. Well, ok, I'll try but honestly what works is often times not something another querier can repeat. There's no formula.
And remember: take advice from the people who are READING your queries, not anyone else. I see bad advice from writers, and editors, and god help us all MFA professors about how to write queries. Some of it's so bad I want to starting knocking heads with a cluestick. There are lots of agents out there talking about how they read queries and things to avoid. Pay attention to them.
And how many antagonists do you have? Maybe you focus there. Try something new and different. Good luck!