You have to merge it with the ships tgl.
BCUT does that for you (if memory serves), but the ship should still work without it, you will just get a couple of ??? on the screen when you use it (instead of the description/name).
IIRC Neither BCMP/BCMI did automatically patch the ships.tgl during ship installation. Process had to be triggered manually. I think only BCMP could patch ships.tgl, and didn't that cause corrupt ships.tgl (under certain conditions :?)?
I do recall a few problems regarding that, I just cannot remember which.
In fact didn't BCMI just extract the tgls's in the bcmod and that's it, the patching never was implemented?
While on subject, which of these had zero-byte file problems in BCMod packages?
I did write TGL editor for BCUT, even made it to attempt to fix and read those corrupt tgls. But still it has to be manually added like in BCMP (additionally patched). All of the focus on BCUT based descriptions went into them actually being placed in the ships plugin and easily editable.
With all the work which went on plugin based descriptions I should really implement a converter so that people can point to the tgl and patch the ships plugin so that the data is added in it.