Reciprocity agreements exist between many states for a Contractor License
The reciprocity agreements allow contractors licensed in certain states to obtain a license in another state without having to take the state trade exam. Sometimes the business and law is also waived. However, most of the time it is not.
The most important aspect is that an exam is required in the state you are licensed in. When it comes to reciprocity the important thing to remember is state jumping is not allowed. This means you cannot obtain a license by reciprocity then turn around and get reciprocity into another state using that license.