I read this short story in elementary school, 15-20 years ago. It was a small book, similar to Apple Paperbacks, but I've combed through lists of all their published works to no avail.
It was written for youth 7-12, and when I read it I think it was age-appropriate. Since it was so long ago, I don't remember many details. I may have read it around '95, but I'm not sure when the book was written. Likely no earlier than the mid-80s, as the book mainly revolves around a boy who has a home computer.
The story involves a young boy talking to someone on his computer. As far as I recall, all communication is done through text. The boy types questions, and receives responses back in kind.
The boy figures out he's talking to an alien that needs his help.
The only significant detail I can remember is that the alien mentions something about how all of Earth's animals would react to the alien's presence, and even the most "docile" of creatures, the earthworm, would be a danger to it. It never explains how it would be a danger to it, which I remember bothering me. (I also believe that this was the first time I read the word "docile".)
Update: I believe the worm explanation was the reason the alien gave for not being able to do stuff himself and needing the boy's help.
I think the boy ended up helping send some sort of signal to the alien's home planet so that they could pick him up? I think he may have involved one of his friends.