Iran and Saudi Arabia have indeed reached an agreement to restore diplomatic ties after years of hostility. The fact that China brokered the deal is significant, as it suggests that major powers are taking an active role in trying to reduce tensions in the region.
The agreement to respect the sovereignty of states and not interfere in internal affairs is a positive step, as it could potentially help to reduce the risk of conflict in the region. However, it remains to be seen how this agreement will be implemented in practice, and whether it will lead to a lasting improvement in relations between Iran and Saudi Arabia.
It is also worth noting that there are likely to be ongoing disagreements between Iran and Saudi Arabia on a range of issues, including their respective positions on the conflicts in Syria and Yemen. Nonetheless, the fact that they have agreed to resume diplomatic relations and re-open embassies is a significant development, and one that could have positive implications for the wider region.