Connector references add a small, fixed cost
A turn that pulls in a connector reference, an email, a Notion page, a GitHub repository, a Linear issue, adds one resolution step at the point your message is actually sent, fetching the referenced content server-side before the model ever sees it.
This resolution step is a small, fixed cost that happens once near the very start of the turn, not something that scales up with how long or complex the rest of the turn ends up being afterward.
See Connectors for exactly what gets sent when you attach a reference this way, and why the resolution happens server-side rather than tCode fetching the content itself.
This cost does not scale with the size of the referenced item either; a short email and a long design document both pay roughly the same fixed resolution cost, since it is a single lookup regardless of how much content comes back from it.
Attaching more than one reference is not possible in a single message, covered in Usage examples, which also means this fixed cost is paid at most once per turn, never compounded by multiple attachments.