Exact ray tracing is the fundamental tool of geometric optics, it constitutes the foundation on which aberration theory and, therefore, optical design is based. We present the KrakenOS, a Python library focused on the accuracy of ray tracing and the generation of systems composed by optical surfaces with arbitrary shapes and orientations, as well as a compendium of practical examples for the use of our library. We describe a series of quality tests to compare the results obtained from ray tracing with KrakenOS with respect to those obtained with the commercial software Zemax. Among the performance computations, we include the final intersection coordinates with optical surfaces, the resulting director cosines, the calculation of surface-to-surface length of the optical path, the energy of the transmitted and reflected resulting rays, Zernike standard coefficients from wavefront fitting, and a comparison of the resulting intersection coordinates with a larger optical system. The difference between our results and those of Zemax is of the order of 9.0  ×  ^{10  −  8} mm, demonstrating that KrakenOS can be used in industrial or scientific work with high precision requirements for simple and very complex optical configurations.