# Chain helpers

On-chain Funding → Trading and Funding withdraw helpers.

Module: `chain` (Python `polyester.chain`, Go `chain`, Rust `polyester::chain`).

**Not ConnectRPC.** Helpers encode calldata / UserOps for:

- Funding → Trading (`TradingGateway.deposit`)
- Funding → external (`FundingAccount.withdrawToChain`) plus Zipper fee quotes
- Allowlist / guard-related encoders where exposed

Testnet constants: `POLYESTER_TESTNET_ENVIRONMENT`.

> **Owner key**
>
> Smart-account helpers take a caller-supplied owner EOA private key. Never commit real keys.

Guide: [Deposits & withdrawals](https://testnet.polyester.com/docs/sdk/go/guides/deposits-and-withdrawals).