Not every cue belongs everywhere. Two declarative frontmatter fields scope any cue or blank: on-host: / not-on-host: pick which integrations load it, and on-site: / not-on-site: (Chrome) pick which websites.
Host scoping
By default everything advertises itself to every host and simply fails visibly where a capability is missing: a shell-script blank can't run in a browser, so Chrome skips it. Declare on-host: chrome, claude-code to be explicit, or not-on-host: shell to subtract.
Site scoping in Chrome
Entries accept an exact hostname (reddit.com), a wildcard (*.reddit.com, covering subdomains and the bare domain), or a hostname plus path prefix (reddit.com/r/claudeai). not-on-site is checked first, an empty on-site means everywhere, and single-page apps re-evaluate on navigation, so scoping holds as you move around a site.
Why it matters
A work-jargon cue scoped to your ticketing site, a blank that only exists in your terminal: scoping is what makes one shared config usable across your whole environment.
Related: Write your own cue · Inline AI in Chrome · GitHub repo