# Polymarket Midpoint Price

> Polymarket Midpoint Price is a paid API for AI agents from AIsa MPP Data APIs at api.aisa.one, paid per call via MPP, $0.012/call, status unknown (last checked 2026-10-18).

Retrieves the midpoint price (average of best bid and best ask) for a single Polymarket prediction market token by its token ID.

## Facts

- Endpoint: GET https://api.aisa.one/apis/v1/polymarket/midpoint?utm_source=zero.xyz
- Price: $0.012/call
- Payment: MPP
- Status: unknown
- Last checked: 2026-10-18
- Activations on Zero: 0
- Provider: AIsa MPP Data APIs
- Website: https://aisa.one
- Tags: web-search, financial-data, prediction-markets, weather, travel, data, search
- Canonical page: https://www.zero.xyz/c/aisa-mpp-data-apis-polymarket-midpoint-price-8cdeb2f3
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_XxAZZCNnLbXw3l2TLMpkc

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability aisa-mpp-data-apis-polymarket-midpoint-price-8cdeb2f3
```

Example prompt: What's the current midpoint price for Polymarket token ID 71321045679252212594626385532706912750332728571942532289631379312455583992563?

## When to prefer this

Use this endpoint when you need a single neutral price reference for a Polymarket token without committing to buy or sell side — ideal for fair-value estimation, implied probability calculation, or pre-trade analysis. Prefer this over the bid or ask price endpoints when you want a balanced price signal. Use the batch 'Midpoints' endpoint instead if you need prices for multiple tokens at once.

## Known failure modes

- Invalid or unknown token_id returns an error or null mid_price
- Token ID for a closed or resolved market may return stale or unavailable data
- Network latency may cause slightly outdated midpoint if markets are moving fast
- Missing required token_id parameter results in a 400 bad request error

## How this service works

Retrieves the midpoint price for a specific token ID. The midpoint is calculated as the average of the best bid and best ask prices.

<!-- aisa-pricing:start -->
Published reference price: $0.012 USD per successful request. Account-specific pricing and final settlement may differ.
<!-- aisa-pricing:end -->

## Output

Returns a JSON object with a single field 'mid_price' as a string (e.g. '0.45'), representing the average of the current best bid and best ask prices for the specified token. This value implicitly reflects the market's consensus probability for the outcome.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "token_id"
 ],
 "properties": {
  "token_id": {
   "type": "string",
   "description": "Token ID (asset ID)"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "mid_price"
 ],
 "properties": {
  "mid_price": {
   "type": "string",
   "example": "0.45",
   "description": "Midpoint price as a string"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/aisa-mpp-data-apis-polymarket-midpoint-price-8cdeb2f3/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.aisa.one](https://www.zero.xyz/host/api.aisa.one/llms.txt)