The five modes

The mode you are in is the safety boundary. Two modes can change your model. Three cannot.

The five modes

Modes are chosen in the task pane.
ModeChanges your modelWhat it is for
AskNoQuestions about the open model, plus live web search. Available on every plan.
PlanNoDrafts a step-by-step build plan for a change without performing any of it.
AgentYesPerforms the change as native SOLIDWORKS feature operations.
DrawingsYesProduces drawings from a part or assembly on your configured standard.
DebugNoDiagnoses rebuild errors, bad sketches and failed features.

What unlocks each mode

Ask is the only mode on Free. Plan, Agent and Debug need any paid plan, so four of the five modes are locked on Free.

Drawings is separate again: it is on for Enterprise, and off by default elsewhere. If you are on a paid plan and Drawings is not selectable, that is why. Plans and limits covers which plan carries which.

Why this is a mode rather than a setting

A read-only mode cannot modify your document at all, not even if you ask it to.

Ask, Plan and Debug can therefore run against a released part or a file checked out by someone else.