Capping agents are frequently used in electrodeposition to support spatially inhomogeneous mass transfer at small scales. As such, chloride ions are known to support the deposition of conically nanostructured nickel layers. This work presents a systematic experimental study of the impact of a capping agent on the electrochemical growth of conically-shaped nickel deposits. Furthermore, a modeling approach on the scale of cones for numerical simulations of electrodeposition with capping agents is provided for the first time to give deeper insight on how the capping agent influences the local growth of the deposit. The growth rates of the nano-cones obtained numerically are compared with experimental data, and a good agreement is found. The impact of the capping agent concentration, the deposition time, the electrolyte temperature and the current density are investigated systematically, and optimum conditions for conical growth are derived.