Jekyll is an editor for Nintendo's GameCube- and Wii-era model files, BMD and BDL. Jekyll is NOT a model converter on its own; it does not generate vertex and geometry data. Instead, it provides facilities for editing the smaller bits of information within the models, such as the metadata for joints and geometry. It also contains a material editor, allowing for the modification or creation of a model's materials.
Initial importing of model data is accomplished via J3DConv, which specializes in glTF models.