panties+bra, bikini and sports panties+bra are visually similar, but functionally different. You simply have to tag by context.
- Is the person in the bed, brushing teeth, undressing, or do you see the clothing under a skirt? Likely underwear.
- Is the person at the beach, with others who are wearing one-piece swimsuits, having a beach ball, towel, sun screen, or the like? Likely swimwear.
- Is the person at the gym, doing exercises, holding weights, at some workout machine, wearing sweatbands or shoes? Likely sportswear.
If there’s little context to go by, there’s more you can look at to determine: if the outfit has a bow, or a heart/striped pattern, it’s more likely underwear. If the outfit has a triangle-bra, underboob, or shiny in style, it’s likely swimwear. Sports panties is the less common variant, so this one usually requires context.
Plus check the tags on the source, it might say underwear, bikini, sportswear, and that can also help.