Mini Dragon is an ONA consisting of 2 minutes videos based on the original series, Kobayashi-san Chi no Maid Dragon. I gave the original series a high 6 (mal score 6) because whilst I enjoyed parts of it, I did find Kobayashi herself to be somewhat annoying and that dropped its score by a bit.
On the other hand, I really enjoyed Mini Dragon, as short as it was. Tohru's 3D model in the op was to-die-for. So, so cute. Lots of points for that. The actual story's themselves were nothing remarkable but nice nonetheless. Great to see the rest of the cast too. I gave Mini Dragon a high 7 (mal score 7) and I don't think that will change.
Also, it got me excited for Kobayashi-san Chi no Maid Dragon S, the sequel, coming out this summer.
It doesn't take too long, so if you've watched and liked the prequel, give Mini Dragon a go!