Clients used to interact with Terra Blockchain from Rust. It can be used directly in CosmWasm smart contracts or from an external blockchain API.
Add terra-proto-rs into the Cargo.toml from your smart contract with default-features to false that way you avoid importing libraries that will make your smart contract fail:
Cargo.toml
terra-proto-rs = {version = "3.0.1", default-features = false}