A script is a JSON list of commands, the same ones the UI runs:
{"commands": [
{"command": "sketch.create", "params": {"plane": "XY"}},
{"command": "sketch.rectangle.two_point", "params": {"p0": [0, 0], "p1": [40, 30]}},
{"command": "solid.extrude", "params": {"distance": 20}},
{"command": "solid.fillet", "params": {"edges": [[0, 0, 10]], "radius": 3}}
]}Run one with solidcraft-cli run script.json --out part.step; see building and the command list.