Question on how to understand if you need permission to use a repeater

[WSFA388]

I'm new to GMRS and am looking to use a repeater.  It is not clear to me when you can just use a repeater vs asking for permission.  Could someone explain please. There seems to be to be more than one site that lists repeaters.  What is the best way to understand that a repeater is available?  Thanks!

[WRXB215]

If the tones are listed publicly, it's probably "open" but if they are not, you should ask for permission from the owner. If the owner grants permission, he will send the tones.

[WSFA388]

Thank you that is helpful.

[amaff]

Wouldn't be the first time that a "private" repeater's tones were readily available.

If it's not really explicit that it's an open system and go ahead and use it, it's good etiquette to at least ask (even if that's keying up, identifying yourself, and saying you're looking for permission to use it and, if the owner's not on, if anyone could put you in touch.