Sophistication of verification techniques ensures Iran will be caught if they try and cheat on the agreement
Basic technical capabilities to detect violations of commitments like those Iran would make under a comprehensive nuclear deal have improved significantly since 1994. This augments the deterrence of cheating, including by heightening the probability that such cheating could be detected in time to allow military interdiction.
Moreover, the proposed agreement to monitor the entire supply of specified materials and technology going to Iran and to limit Iran’s procurement to a declared channel eases the burden of verification and intelligence gathering and assessment. Any procurement that was detected outside the monitored supply chain and declared channel would presumably be deemed a violation of the agreement. Unlike today, intelligence analysts and policymakers would not have to debate whether a detected activity actually signifies a violation of the NPT or of any other international nonproliferation norm or guideline.
The agreement is based on verification, not trust. According to the U.S. fact sheet, Iran has agreed to accept the IAEA’s Additional Protocol as well as several even more intrusive monitoring and inspection measures that will provide high confidence that Iran is not making bomb material at its declared nuclear facilities and will significantly strengthen the ability of inspectors to detect clandestine facilities