Header
Also called HTTP header
A labelled line of extra information on a request or response, such as Content-Type: application/json. Names ignore upper and lower case. Many travel with every request, and you never see them unless you look.
One header is often the whole fix, and it can save an agent writing a page of code: caching, content type, a redirect, a login challenge. Ask for it by name. Code running in the page can't set them all either, so some header bugs can't be fixed in the frontend at all.
Say it to your agent
“Add Cache-Control: no-store and Content-Type: application/json to every response from /api/account, and add a test that makes a real request and fails if either header is missing.”