# NEXUS Arbitrage Price Comparison

> NEXUS Arbitrage Price Comparison is a paid API for AI agents from nexus-agent-xa12.onrender.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-13).

Compares prediction market prices between Kalshi and Polymarket for Fed, BTC, and CPI markets to surface arbitrage opportunities

## Facts

- Endpoint: GET https://nexus-agent-xa12.onrender.com/arb/check
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/nexus-arbitrage-price-comparison-e202e743
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_pQQFwMTJFJCI2WLtyEtE2

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 nexus-arbitrage-price-comparison-e202e743
```

Example prompt: Check if there's a price spread between Kalshi and Polymarket for Fed, BTC, and CPI markets — I want to see which platform is cheaper and by how much.

## When to prefer this

Use this endpoint when you need real-time price spread data between Kalshi and Polymarket for Fed rate, BTC, or CPI prediction markets and want to identify arbitrage opportunities. Prefer this over general financial data APIs when the specific goal is cross-platform prediction market comparison with per-call micropayment pricing via USDC.

## Known failure modes

- Invalid or unsupported market name returns an error or empty result
- Payment failure via x402 USDC returns 402 status blocking data access
- Service unavailable on Render cold start causes timeout or 503
- Empty markets query param may return all or no markets depending on default behavior

## How this service works

Pay-per-call financial data. Streamable HTTP MCP. x402 USDC on Base. Not financial advice.

## Output

Returns a list of market comparisons, each with the spread amount, the direction indicating which platform (Kalshi or Polymarket) has the lower price, and the exact prices on each platform for the requested markets (Fed, BTC, CPI).

## 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",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [],
     "properties": {
      "markets": {
       "type": "string",
       "description": "Comma-separated markets: Fed,BTC,CPI"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "markets": [
   "Fed"
  ],
  "comparisons": [
   {
    "market": "Fed",
    "spread": 27.55,
    "direction": "kalshi_yes_cheaper",
    "kalshi_price": 42,
    "polymarket_price": 69.55
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/nexus-arbitrage-price-comparison-e202e743/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from nexus-agent-xa12.onrender.com](https://www.zero.xyz/host/nexus-agent-xa12.onrender.com/llms.txt)