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

# Guardrails

> Server-side risk limits checked before any order reaches the venue.

Neither Kalshi nor Polymarket gives you a max order size, a daily-loss limit, or
a kill switch. Mithril checks **every** order against your limits **before** it's
signed and sent — a rejection means the order never reached the exchange.

## The limits

Set at the workspace level and optionally overridden per subaccount (the
effective limit is the tighter of the two):

| Limit                     | Enforces                                          |
| ------------------------- | ------------------------------------------------- |
| `max_order_notional`      | Largest single order, in quote currency           |
| `max_position_per_market` | Cap on exposure to one market                     |
| `max_total_notional`      | Cap on total open exposure                        |
| `slippage_bps`            | Worst execution slippage tolerated                |
| `max_concentration_bps`   | Cap on how concentrated one position can be       |
| `max_open_orders`         | Ceiling on resting orders                         |
| `max_daily_loss`          | Circuit breaker on realized loss for the day      |
| `kill_switch`             | When `true`, rejects **all** new orders instantly |

## Read your limits

<CodeGroup>
  ```bash cURL theme={null}
  curl https://api.trymithril.com/v1/risk_limits/sub_... \
    -H "Authorization: Bearer $MITHRIL_API_KEY"
  ```

  ```python Python theme={null}
  limits = s.get(f"{BASE}/v1/risk_limits/{sub_id}").json()
  print(limits["max_order_notional"], limits["kill_switch"])
  ```
</CodeGroup>

```json theme={null}
{
  "id": "rl_...",
  "workspace_id": "ws_...",
  "subaccount_id": "sub_...",
  "max_order_notional": "250",
  "max_position_per_market": "1000",
  "max_total_notional": "5000",
  "slippage_bps": 300,
  "max_concentration_bps": 4000,
  "max_open_orders": 20,
  "max_daily_loss": "1000",
  "kill_switch": false,
  "created_at": "2026-07-16T14:00:00Z",
  "updated_at": "2026-07-16T14:30:00Z"
}
```

<Note>
  Notional fields are decimal strings; `"0"` (or an omitted field) means
  **unlimited**. The `PUT` body accepts the same fields —
  `max_order_notional`, `max_position_per_market`, `max_total_notional`,
  `slippage_bps`, `max_concentration_bps`, `max_open_orders`, `max_daily_loss`,
  `kill_switch`.
</Note>

## Update a limit

```bash theme={null}
curl -X PUT https://api.trymithril.com/v1/risk_limits/sub_... \
  -H "Authorization: Bearer $MITHRIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "max_order_notional": "250", "max_daily_loss": "1000" }'
```

## The kill switch

Flip one boolean to halt trading on a subaccount — nothing new gets through
until you flip it back:

```bash theme={null}
curl -X PUT https://api.trymithril.com/v1/risk_limits/sub_... \
  -H "Authorization: Bearer $MITHRIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "kill_switch": true }'
```

## What a rejection looks like

Submit something over your limit and the order is refused with `409` and a clear
reason — this is the guardrail doing its job:

```json theme={null}
{
  "error": {
    "code": "risk_limit_exceeded",
    "message": "order notional 40000 exceeds max_order_notional 250",
    "request_id": "req_..."
  }
}
```

<Tip>
  This is exactly what `python 03_guardrails.py` demonstrates — it submits a
  deliberately oversized order and prints the rejection.
</Tip>

<Card title="Next: Orders" icon="arrow-right-arrow-left" href="/guides/orders">
  Place, track, and cancel — now that the guardrails are set.
</Card>