This is a counterpart for substrate-parser that allows construction of extrinsics based on metadata supplied. See an example of its use in Lempi project
substrate-parser + substrate-constructor system is
- much leaner (does not pull all multitude of sp-* crates, only minimal ones) - thus is more portable,
- is more modular,
- designed for clients and visualization,
- has more ideomatic extrinsic construction flow.