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

# Market Open Interest

> Onchain open interest for a specific market.

Returns the current open interest for a specific market, sourced from onchain data. Enriched with market metadata.

## Request

```
GET /v2/onchain/markets/{condition_id}/oi
```

| Parameter      | Type   | Location | Description                                     |
| -------------- | ------ | -------- | ----------------------------------------------- |
| `condition_id` | string | path     | Market condition ID (0x-prefixed, 64 hex chars) |

## Response

```json theme={null}
{
  "condition_id": "0x8180fee481707671aa45de84a9c3740ab607f3f2643b456e0380afb02d12cf7d",
  "source": "onchain",
  "found": true,
  "market": "Bitcoin Up or Down - March 28, 10:55AM-11:00AM ET",
  "slug": "btc-updown-5m-1774709700",
  "image": "https://polymarket-upload.s3.us-east-2.amazonaws.com/BTC+fullsize.png",
  "open_interest_usdc": 393.153937
}
```

| Field                | Type    | Description                          |
| -------------------- | ------- | ------------------------------------ |
| `found`              | boolean | Whether the market was found onchain |
| `market`             | string  | Market question                      |
| `slug`               | string  | Market slug                          |
| `image`              | string  | Market image URL                     |
| `open_interest_usdc` | number  | Current open interest in USDC        |

## Example

```bash theme={null}
curl "https://api.polynode.dev/v2/onchain/markets/0x8180fee481707671aa45de84a9c3740ab607f3f2643b456e0380afb02d12cf7d/oi" \
  -H "x-api-key: YOUR_KEY"
```


## OpenAPI

````yaml GET /v2/onchain/markets/{condition_id}/oi
openapi: 3.1.0
info:
  title: PolyNode API
  description: >-
    Real-time Polymarket data API with decoded mempool settlements, OHLCV
    candles, and full Polygon JSON-RPC proxy.
  contact:
    name: PolyNode
    url: https://polynode.dev
  license:
    name: ''
  version: 2.0.0
servers:
  - url: https://api.polynode.dev
    description: Production
security:
  - api_key: []
paths:
  /v2/onchain/markets/{condition_id}/oi:
    get:
      tags:
        - Onchain
      summary: Market open interest (onchain)
      description: Onchain open interest for a specific market.
      operationId: onchain_market_oi
      parameters:
        - name: condition_id
          in: path
          required: true
          schema:
            type: string
          description: Market condition ID
      responses:
        '200':
          description: Open interest
        '401':
          description: Unauthorized
      security:
        - apiKey: []
components:
  securitySchemes:
    api_key:
      type: apiKey
      in: header
      name: x-api-key

````