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

# watchTrades

> Stream real-time trade updates for a single outcome via WebSocket

<Info>
  **WebSocket endpoint** — This method uses WebSocket streaming, not HTTP. Connect to `wss://api.pmxt.dev/ws?apiKey=YOUR_KEY` (hosted) or `ws://localhost:3847/ws` (local server).
</Info>

Supported venues: `polymarket`, `kalshi`, `limitless`, `opinion`, `polymarket_us`, `myriad`, `gemini-titan`, `rain`, `hunch`.

## Parameters

| Parameter   | Type   | Required | Description                   |
| ----------- | ------ | -------- | ----------------------------- |
| `outcomeId` | string | Yes      | The outcome token ID to watch |

## Response

Returns a `Trade[]` array each time new trades occur:

| Field       | Type   | Description                       |
| ----------- | ------ | --------------------------------- |
| `id`        | string | Trade ID                          |
| `timestamp` | number | Unix timestamp in milliseconds    |
| `price`     | number | Trade price (0–1 probability)     |
| `amount`    | number | Number of contracts               |
| `side`      | string | `"buy"`, `"sell"`, or `"unknown"` |

## Usage

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

  exchange = pmxt.Polymarket(pmxt_api_key="YOUR_PMXT_API_KEY")

  while True:
      trades = exchange.watch_trades("OUTCOME_ID")
      for trade in trades:
          print(f"{trade.side.upper()} {trade.amount} contracts @ {trade.price:.1%}")
  ```

  ```javascript JavaScript theme={null}
  import { Polymarket } from "pmxtjs";

  const exchange = new Polymarket({ pmxtApiKey: "YOUR_PMXT_API_KEY" });

  while (true) {
    const trades = await exchange.watchTrades("OUTCOME_ID");
    for (const trade of trades) {
      console.log(`${trade.side.toUpperCase()} ${trade.amount} contracts @ ${(trade.price * 100).toFixed(1)}%`);
    }
  }
  ```

  ```json WebSocket theme={null}
  // → Subscribe
  { "id": "req-1", "action": "subscribe", "exchange": "polymarket", "method": "watchTrades", "args": ["OUTCOME_ID"] }

  // ← Data event
  {
    "event": "data",
    "id": "req-1",
    "method": "watchTrades",
    "symbol": "OUTCOME_ID",
    "source": "polymarket",
    "data": [
      {
        "id": "trade-abc123",
        "timestamp": 1778450010713,
        "price": 0.42,
        "amount": 100,
        "side": "buy"
      }
    ]
  }
  ```
</CodeGroup>

## Use cases

### Trade volume tracker

Monitor real-time trading volume on a market:

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

  exchange = pmxt.Polymarket(pmxt_api_key="YOUR_PMXT_API_KEY")
  total_volume = 0

  while True:
      trades = exchange.watch_trades("OUTCOME_ID")
      for trade in trades:
          total_volume += trade.amount
          print(f"Trade: {trade.side} {trade.amount} @ {trade.price:.1%} | Total volume: {total_volume}")
  ```

  ```javascript JavaScript theme={null}
  import { Polymarket } from "pmxtjs";

  const exchange = new Polymarket({ pmxtApiKey: "YOUR_PMXT_API_KEY" });
  let totalVolume = 0;

  while (true) {
    const trades = await exchange.watchTrades("OUTCOME_ID");
    for (const trade of trades) {
      totalVolume += trade.amount;
      console.log(`Trade: ${trade.side} ${trade.amount} @ ${(trade.price * 100).toFixed(1)}% | Total: ${totalVolume}`);
    }
  }
  ```
</CodeGroup>