The design and performance optimization of future nanocatalysts will depend on our understanding of adsorbate-metal interactions. Using first principle calculations, we identify suitable descriptors, namely, the coordination number and curvature angle of the surface Au atoms, capable of predicting the CO binding strength on every site of Au nanoparticles. Our results unravel how the size, shape, and symmetry of nanoparticles affect their electronic properties and, consequently, their interaction with CO. Importantly, these descriptors can be successfully applied to other metals using structural inputs from experiments and/or molecular modeling.