I bought this tool for dandelions, and I have found it to be the best dandelion puller ever. It works on weeds that grow from a central point. By positioning the prongs over the very center of the dandelion, and shoving the tool into the ground with a little pedal provided for that purpose, you then give the tool a sideways twist, and the dandelion pops right out, held within the prongs. It doesn't matter if it's in tall grass or not; the only thing that's essential is that it be centered over the weed. Of course, the ground has to be reasonably soft, but that would be true for any such tool.
This tool really saves my back, because you don't have to been over alot. Mind is sturdily made, and has lasted for several years of use. I would recommend this tool to anyone!