MoSART (Molecular Structure Analysis and Refinement Tool) is designed for computing biomolecular structure from NMR data. The goal of the project is to create an easily extensible package that will broaden the community of developers of new approaches to computation of biomolecular structure from NMR data. A key feature is support for low-resolution (two particles per residue for proteins, 3/4 particles per residue for nucleic acids) force fields, useful when geometrical restraints are sparse. These facilitate determination of the overall fold during early stages of an NMR investigation, or starting points for hierarchical structure determination. Future plans include additional support for low resolution geometrical constraints derived from NMR and chemical footprinting to support membrane protein structure determination.