035 has beans :0!?
Strap in, this is a long one.
So, I'm fond of bugs and it's why I lean in on Alagaddans being sort of insect-like, both in appearance and in culture ( you're probably too young to be reading my fanfics, so the PG explanation is that Alagaddan culture is 'roles, not rules'. Everyone has a set role they're made to play, like workers and drones and queens in a beehive. It looks chaotic to an outsider, but the Alagaddans are stuck in their roles. )
On to chitin. In SCP-2264, the Alagaddans' clothing is referred to as 'chitinous' and in SCP-6624 the masks are 'porcelain-like' but 'more closely related to chitin'. Now, when you're getting into details, people usually get chitin wrong. See, hard chitin like a beetle's shell is modified chitin, it's chitin with some other stuff mixed in to make it hard. Pure chitin is soft, flexible, and tough. If you've ever pet a caterpillar, that's what pure chitin is. ( Metaphysician got it right, assuming the Alagaddans were wearing soft clothes and not armour, and I'm pretty sure the Foundation agents would have mentioned it if the Alagaddans were wearing armour. )
So bugs have a problem - with their hard shells, how to they feel things? Bugs have tiny hairs that poke out through their shells. Like if you put a little football helmet on a cat so their whiskers could still poke through. But Alagaddans are sensual beings - not just 'sensual' as 'sexy' but 'sensual' as 'luxurious'. Being hard-shelled all over with just tiny hairs to feel with doesn't feel luxurious to me.
Since Alagaddans are made-up other-dimensional beings that don't conform to Earthly science, you could just say their shells have tactile senses and call it a day. I do that to a degree, I do let their hard shells feel. However, it's also hard to pick things up without soft, grippy fingers.
So I ended up giving the Alagaddans mixed hides: Underskin, which is pitch black and soft, made of pure chitin. Plating, which is white, made of chitin modified with porcelain. Mask, which is made of porcelain ( well, magic porcelain. ) And since I want them to be able to feel things and pick things up, I only put plating on the backs of their hands and feet, leaving the palms to be underskin.
tl;dr: Alagaddans have beans because Science.
