I actually quite liked it. Take the rest of this as my attempt to suggest things that should be fixed to get it up to speed.
1. "SCP-XXXX is stored in a 6m x 6 concrete room." First, dimensions have to be in three dimensions with units after each one, like ('6m x 6m x 6m'). Second, nothing in the article suggested there was any specific reason why it had to be a room of that exact size. It's more economical for the Foundation if you just say "in a concrete room at least _m x _m x _m in size"; state minimum requirements rather than exact ones.
2. "Should SCP-XXXX breach containment, a task force utilizing chemical herbicides" — Herbicides? To kill fungus? Wouldn't you use mycocides? I'm literally asking because I have no idea if herbicides would kill freestanding fungus.
3. "SCP-XXXX is a mammal measuring 55cm head to body"; you mean something like "head to toe", but you can just say "55 cm in length" and get the same result with better clinical tone.
4. Neither of your addenda should really be addenda; those should be part of the description. They're pretty essential parts of what the SCP is.
Those are the things that most evidently popped into my head. Feel free to look at it further.
