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

# Close to Bond

> Fire a webhook when a trade prints at a near-certain-outcome price.

<Note>
  **Event:** `close_to_bond` \
  **Cost:** 0.2 credits per delivery
</Note>

The `close_to_bond` callback fires when a trade occurs at the near-certain end of a market (for example an outcome trading at ≥ 95¢ or ≤ 5¢). The full callback schema is in the auto-generated [Close to bond callback](/api-reference/webhook-callbacks/close-to-bond-callback) reference; this page explains the one part the schema can't show on its own: how the price filters define the zone.

## Defining the bond zone

The bond zone is defined entirely by how you combine `min_price` and `max_price`. The **relationship between the two values** selects one of four modes:

| You set                    | Mode             | Fires when                                     | `bond_side`         |
| -------------------------- | ---------------- | ---------------------------------------------- | ------------------- |
| `min_price` only           | Single high edge | `price ≥ min_price`                            | `"high"`            |
| `max_price` only           | Single low edge  | `price ≤ max_price`                            | `"low"`             |
| Both, with **`min < max`** | Bounded range    | `min_price ≤ price ≤ max_price`                | `"high"`            |
| Both, with **`min > max`** | Two edges        | `price ≥ min_price` **or** `price ≤ max_price` | `"high"` or `"low"` |

<Warning>
  **`min < max` is a band, not a bond.** If you set `min_price: 0.75` and `max_price: 0.90`, you do **not** get "fires above 90% or below 75%". Because `min < max`, it switches to bounded-range mode and fires only when the price lands **inside** the 75–90% band. To alert on the two near-certain extremes, you must set `min > max` (see below).
</Warning>

## Alerting on near-certain outcomes

To get notified when an outcome becomes near-certain in **either** direction (at or above 90% **or** at or below 10%), set `min_price` **higher** than `max_price`:

```json theme={null}
{
  "min_price": 0.90,
  "max_price": 0.10
}
```

Because `0.90 > 0.10`, this is read as two separate edges. A trade at 96¢ fires with `bond_side: "high"`; a trade at 4¢ fires with `bond_side: "low"`. For a single edge, set just one of the two.

## How price is read

* The traded position's own `price` is used: the price of the exact outcome token (`position_id`) that printed.
* Trades at a price of exactly `0` or `1` are skipped, since there is no remaining risk to alert on.
* `price` is on a `0.0`–`1.0` scale (so 95¢ = `0.95`).

## Picking the right side

On a binary market, "YES at ≤10%" and "NO at ≥90%" are the **same** event priced from opposite tokens. If you add `position_outcome_indices: [0]` you will only ever see trades that print on the **Yes/Up** token (index `0`); trades on the No token (index `1`) won't fire even when they hit the same bond zone. Omit `position_outcome_indices` to catch the zone regardless of which side the trade prints on.

## Subscription filters

Add these to the `filters` object when you create the subscription. At least one of `min_price` or `max_price` is required.

| Filter                      | Type      | Description                                                                                   |
| --------------------------- | --------- | --------------------------------------------------------------------------------------------- |
| `min_price`                 | number    | High-edge / lower bound of the zone, `0.0`–`1.0`.                                             |
| `max_price`                 | number    | Low-edge / upper bound of the zone, `0.0`–`1.0`.                                              |
| `condition_ids`             | string\[] | Restrict to specific markets (max 500).                                                       |
| `position_ids`              | string\[] | Restrict to specific outcome tokens (max 500).                                                |
| `outcomes`                  | string\[] | Restrict by outcome name, e.g. `["Yes", "No"]` (max 500).                                     |
| `position_outcome_indices`  | number\[] | Restrict by outcome index: `0` (Yes/Up) or `1` (No).                                          |
| `event_slugs`               | string\[] | Restrict to specific events (max 500).                                                        |
| `tags`                      | string\[] | Restrict to markets carrying any of these tags or category names, case-insensitive (max 500). |
| `series_slugs`              | string\[] | Restrict to markets in any of these series by slug, case-insensitive (max 500).               |
| `exclude_shortterm_markets` | boolean   | Exclude short-term Up/Down markets.                                                           |

<Tip>
  **Scope by market taxonomy.** `tags` matches a market's own tags **or** its category, given as the display label shown on Polymarket (for example `"Sports"`, `"Politics"`, or `"FIFA World Cup"`), not a slug. `series_slugs` matches the market's parent series by slug (for example `"nba-finals"`). Both are case-insensitive, accept up to 500 values each, and an empty or omitted list applies no taxonomy restriction.
</Tip>

For a worked walkthrough across both webhooks and websockets, see the [Bond-zone alerts guide](/guides/bond-zone-alerts).