> ## Documentation Index
> Fetch the complete documentation index at: https://pmxt-sync-hosted-docs.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Signing Orders

> What the SDK does for you, and how to plug in a custom signer if you need one.

Hosted trading writes are authenticated by an **EIP-712 typed-data signature** computed locally on your machine. PMXT never sees your private key. The `pmxt_api_key` authenticates you to PMXT; the signature authenticates the order to the venue's on-chain settlement contract.

## What the SDK does for you

Pass `private_key` to the exchange constructor and you're done. The SDK auto-wraps it into a local signer (`EthAccountSigner` in Python, `EthersSigner` in TypeScript), builds the typed-data payload for the right venue, signs locally, and submits the signature. You never see the typed-data shape.

<CodeGroup>
  ```python Python theme={null}
  import pmxt

  client = pmxt.Polymarket(
      pmxt_api_key="pmxt_live_...",
      wallet_address="0xYourWallet...",
      private_key="0xYourPrivateKey...",
  )

  order = client.create_order(
      market_id="2eeb03dc-404b-41d5-bc57-6aeb37927ae6",
      outcome_id="a114f052-1fd1-4bcd-b9cf-de019db81b67",
      side="buy",
      order_type="market",
      amount=5.0,
      denom="usdc",
      slippage_pct=30.0,
  )
  ```

  ```typescript TypeScript theme={null}
  import { Polymarket } from "pmxtjs";

  const client = new Polymarket({
    pmxtApiKey: "pmxt_live_...",
    walletAddress: "0xYourWallet...",
    privateKey: "0xYourPrivateKey...",
  });

  const order = await client.createOrder({
    marketId: "2eeb03dc-404b-41d5-bc57-6aeb37927ae6",
    outcomeId: "a114f052-1fd1-4bcd-b9cf-de019db81b67",
    side: "buy",
    type: "market",
    amount: 5,
    denom: "usdc",
    slippage_pct: 30,
  });
  ```
</CodeGroup>

### Single-signature vs dual-signature flows

Most hosted writes are **single-signature** — one EIP-712 payload, surfaced as `built.raw["typed_data"]`. This covers:

* Polymarket buys and sells — `OrderParams` on the Polygon `PreFundedEscrow` domain.
* Opinion BUY — `CrossChainOrderParams` on the Polygon `PreFundedEscrow` domain (the BSC delivery leg needs no user signature; the user is the recipient).
* Limitless buys and sells — ERC-7683 order on the Polygon escrow domain.

**Opinion SELL is the one dual-signature case.** The user gives up tokens custodied on BSC, so the SDK builds two payloads at once:

* `built.raw["typed_data"]` — `CrossChainSellPayParams` on the Polygon `PreFundedEscrow` domain (the operator's pay leg into the user's Polygon balance).
* `built.raw["pull_typed_data"]` — `CrossChainSellPullParams` on the BSC `VenueEscrow` domain (the operator's pull leg against the user's BSC outcome tokens).

The SDK signs both with the same EVM private key automatically — no extra wiring. The two domains are distinct (`PreFundedEscrow` on chainId 137, `VenueEscrow` on chainId 56) and each signature only authorizes its own chain's leg.

## Why reads only need a wallet address

For reads (`fetch_balance`, `fetch_positions`, `fetch_my_trades`), no signature is required — the `pmxt_api_key` is enough. You can construct a hosted client with only `pmxt_api_key` and `wallet_address` and read hosted state for that wallet:

```python theme={null}
import pmxt

read_only = pmxt.Polymarket(
    pmxt_api_key="pmxt_live_...",
    wallet_address="0xSomeOtherWallet...",
    # no private_key
)
balance = read_only.fetch_balance()  # works
```

<Warning>
  Because reads don't require a signature, anyone with the `pmxt_api_key` can read any wallet's hosted state. Keep the key on the server. See the [trust model](/concepts/hosted-trading#trust-model).
</Warning>

## Advanced: bring your own signer

If your key lives in a hardware wallet, HSM, MPC service, or anything that isn't a raw hex private key, skip `private_key` and inject a custom signer at construction. The SDK uses it transparently for every hosted write — you keep calling `create_order` as usual.

The signer protocol is one method: `sign_typed_data(typed_data: dict) -> hex` (Python) or `signTypedData(typedData): Promise<string>` plus a readonly `address` (TypeScript).

<CodeGroup>
  ```python Python theme={null}
  import pmxt

  client = pmxt.Polymarket(
      pmxt_api_key="pmxt_live_...",
      wallet_address="0xYourWallet...",
      signer=my_custom_signer,  # exposes sign_typed_data(typed_data) -> hex
  )

  order = client.create_order(
      market_id="2eeb03dc-...",
      outcome_id="a114f052-...",
      side="buy",
      order_type="market",
      amount=5.0,
      denom="usdc",
      slippage_pct=30.0,
  )
  ```

  ```typescript TypeScript theme={null}
  import { Polymarket } from "pmxtjs";

  const client = new Polymarket({
    pmxtApiKey: "pmxt_live_...",
    walletAddress: "0xYourWallet...",
    signer: myCustomSigner,  // { address, signTypedData(typedData) -> Promise<hex> }
  });

  const order = await client.createOrder({
    marketId: "2eeb03dc-...",
    outcomeId: "a114f052-...",
    side: "buy",
    type: "market",
    amount: 5,
    denom: "usdc",
    slippage_pct: 30,
  });
  ```
</CodeGroup>

For Opinion SELL's dual-signature flow, the same injected signer is invoked twice (once for the Polygon pay leg, once for the BSC pull leg) — no extra wiring. The SDK's `EthAccountSigner` (Python) / `EthersSigner` (TypeScript) are reference implementations; ethers v6 supports Ledger out of the box, and for MPC see Fireblocks / Privy / Turnkey docs.