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Correct answer: B. It does not load at all, and neither the server nor its tools appear in chat.
Explanation
The principle — The toggle in Customize is a load switch rather than a visibility filter. Disabled servers will not load or appear in chat, so switching one off genuinely takes it out of the run.
Why the key is correct — Turning a server off stops it being started and removes its tools from the surface the Agent can choose from, which is exactly why the toggle is the recommended way to reduce tool clutter or to isolate a misbehaving server. Switching it back on restores it without re-entering any configuration, because the entry in mcp.json is left alone throughout.
Why the others are wrong — A greyed-out entry with a live process behind it would defeat both uses: the tools would still compete for the Agent's attention, and a crashing server would still crash. A half-state where already-registered tools linger until a restart describes a staleness the toggle does not have. And the toggle does not rewrite your configuration; removing the server from Customize is the separate action for that, and it is the route used when you want to reinstall a server to pick up a newer version.
Remember this — Toggle to test. When a run misbehaves and one server is the suspect, switch it off, reproduce, and switch it back on; nothing about the configuration is lost in between.
Sources — Cursor's MCP documentation.
Sources
“Disabled servers won't load or appear in chat.”
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