Let's see ... Syria was just accused of launching chemical weapons. Syria denied the accusation and Putin is standing by Asaad. I'd say this is more than a gesture ... Trump didn't even wait 48 hours ... its jumping the gun without concrete proof and without the consent of Congress!
By "gesture," I mean that if Trump is using this as a one-off to be tough, as opposed to having some broader intent in mind.
As for Congress, I definitely agree that Congress should be brought in, and the heads of the various national security committees were probably consulted and/or informed, which I believe is the standard set in the War Powers Act, in matters of vital national security interest where time is of the essence. (Hence his weasel words on that matter.)
The prospect of another drawn-out fiasco like the one following Obama's stupid "red line" threat is probably part of the reasoning. If it happened again this time (it would) the consequences would be very bad - the world would see Trump being hamstrung by the likes of Schumer, and our reputation would be worse than it was even under Obama.