In reply to Richard Carter:
I've got a Park CT-5 tool in the tool box - it works well, for the few occasions I've used it, which is mainly to shorten a new chain (quick link to join it).
On rides, I carry a ToPeak Mini 18+ tool, which has a built-in chain tool - used that a couple of times and seems fine, if a bit more fiddly.
Can't comment on the CT-6.3 or compatibility with anything higher than 9-speed, although I thought the pin size was the same but the chain was narrower?