How much? Worth it? Names?
Have you searched this forum? There are lots of recommendations.
Here are some discussions with recommendations:
https://community.ricksteves.com/travel-forum/italy/rome-good-tour-company
https://community.ricksteves.com/travel-forum/italy/vatican-museum-guides
https://community.ricksteves.com/travel-forum/italy/questions-for-rome-visit
How much? Worth it? Names?
What country? What city? What type of tour? What are your interests? Full day or part day? For how many people? What makes a tour worthwhile, in your opinion?
A modicum of information would go a long way.
Probably looking for Rome
https://community.ricksteves.com/travel-forum/italy/private-tours-612af93c-a5bc-4580-bb62-63803793b529