I use this site for remodeling advice but also for product purchases, as members of my family are carpenters, woodworkers,plumbers, tile setters and a roofer. How do I know for sure that a tool that is advertised is a good product for the type of trade involved and a good value for the money? Buying on line creates a problem as there is no gift receipt and it involves returning the product which is usually costly.

Any comments will be greatly appreciated.

There are no magic tools. Those on line are simply a new type of gadget that has not made it in the tool store or real world. If it really does work like they say on line, then these tools would be available at your local tool shop.

Buying on line like you said does not provide the comfort in knowing if they will do what they claim.
Your best bet is to find the tool that you want in a local supply company that offers it and touch feel and if at all try before you buy. Once you have done this and can find it cheeper on the internet then you can go ahead. But there is one more issue. Many tool companies will not repair tools not bought at their place. So be sure you can return what ever you buy to be fixed if it breaks. Most likely the ones sold over the net are special. Sort of like the ones The big box stores sell. They have their own specs on how the tool is built. And most if not all repair companies cannot get the parts to fix once they break.
My advice unless you can purhcase off the shelf in a local tool shop, stay away from any expensive tools sold on line that are not available anywhere else. The cheeper ones, you get what you pay for.