[disclaimer: I work on the Computer Vision API] Good examples! It looks like you were using the Image Captioning operation in the Computer Vision API. I would think that, for the cases where the output was not correct, the API returns a low confidence score; it really depends on your scenarios, but, in my own testing, a caption with <40% confidence score is likely to have incorrect info. Now, to explain what's going on a bit better: the vision models behind the API were trained with a large body of images; you can imagine that coat of arms or images of astronauts weren't very prevalent (while images of giraffes or motorcycles were). We continue to improve the vision models over time, so seeing feedback like this on HN (or StackOverflow, or the User Voice forum on Microsoft.com/cognitive) helps!