The justification for depriving someone of their liberty lies solely with the arresting officer. They can base that on whatever they want, as long as they can later justify it to a court.
For example, you might have a trusted informant who could tell you who committed a local burglary, just this on its own could be legitimate grounds to make an arrest. The same informant might walk into a police station and tell the same information to someone else, for that officer, it might not be sufficient to justify an arrest.