Welp, it figures I would find the answer to this right after posting the question, even though I have been stuck for a while…
Archive of version of docs originally linked in answer:
http://code.google.com/chrome/extensions/content_scripts.html
Analog page for Manifest V2 (though see also V3):
https://developer.chrome.com/docs/extensions/mv2/content_scripts/
In manifest.json:
"content_scripts": [
{
"matches": ["http://*.nytimes.com/*"],
"exclude_matches": ["*://*/*business*"],
"js": ["contentScript.js"]
}
],