# Bookproof — Polymarket Market Health & Order Book Intelligence

> Bookproof — Polymarket Market Health & Order Book Intelligence is a paid API for AI agents from bookproof-api.sn95wjq846.chatgpt.site, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14).

Returns real-time Polymarket order book depth, spread, fees, freshness, and executable VWAP data for a given prediction market.

## Facts

- Endpoint: GET https://bookproof-api.sn95wjq846.chatgpt.site/api/v1/market-health
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/bookproof-polymarket-market-health-order-book-intelligence-6d1131d9
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_7pF6nf03DBn1mVxowWe4M

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 bookproof-polymarket-market-health-order-book-intelligence-6d1131d9
```

Example prompt: Check the Polymarket order book health for the 'will-the-fed-decrease-interest-rates-by-25-bps-after-the-july-2026-meeting' market — I need the current spread, best bid and ask, taker fee rate, and whether the book is fresh and not crossed before I place a trade.

## When to prefer this

Use this endpoint when an autonomous agent needs pre-trade intelligence on Polymarket — specifically when fee-aware execution cost, spread, order book freshness, and health checks are required before placing or sizing a trade. Prefer this over generic Polymarket API calls when you need VWAP, imbalance, and fee data in a single response, or when you need to verify that the book is not crossed or stale before committing capital.

## Known failure modes

- Market not found: invalid slug, URL, or token ID returns an error or empty result
- Stale data: health.stale=true indicates the order book hasn't been updated recently
- Crossed book: health.crossed=true means best bid >= best ask, making execution unreliable
- Payment failure: missing or invalid x402 payment header results in 402 response
- Rate limiting: excessive calls without valid payment may be throttled
- Ambiguous search phrase: non-unique market search phrase may resolve to wrong market

## How this service works

Read-only Polymarket depth, spread, fee, freshness, and executable VWAP data for autonomous agents, paid per call with x402.

## Output

Returns a JSON object containing: the market slug, per-outcome order book data (best bid, best ask, spread, 2-cent imbalance), fee parameters (taker rate, exponent, taker-only flag), and a health object indicating whether the book is stale, crossed, or healthy.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "pathParams": {
     "type": "object"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "market"
     ],
     "properties": {
      "market": {
       "type": "string",
       "maxLength": 500,
       "minLength": 2,
       "description": "Polymarket URL, market slug, CLOB token ID, or market search phrase."
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "fee": {
   "exponent": 1,
   "takerOnly": true,
   "takerRate": 0.04
  },
  "books": [
   {
    "spread": 0.01,
    "bestAsk": 0.43,
    "bestBid": 0.42,
    "outcome": "Yes",
    "imbalance2c": -0.12
   }
  ],
  "health": {
   "stale": false,
   "status": "healthy",
   "crossed": false
  },
  "market": {
   "slug": "will-the-fed-decrease-interest-rates-by-25-bps-after-the-july-2026-meeting"
  },
  "service": "bookproof"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/bookproof-polymarket-market-health-order-book-intelligence-6d1131d9/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from bookproof-api.sn95wjq846.chatgpt.site](https://www.zero.xyz/host/bookproof-api.sn95wjq846.chatgpt.site/llms.txt)