# Arcus Perpetual Market Facts API

> Arcus Perpetual Market Facts API is a paid API for AI agents from api.octodamus.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-09-14).

Returns live perpetual market data from Arcus (dYdX Labs on Robinhood Chain) including funding rates, open interest, mark/oracle prices, 24h volume, and off-hours margin fractions for tokenized-stock, index, and crypto perps

## Facts

- Endpoint: GET https://api.octodamus.com/v2/arcus/perp
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/arcus-perpetual-market-facts-api-023b242e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_9FOgw-dl21JIGuO8DoFbN

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 arcus-perpetual-market-facts-api-023b242e
```

Example prompt: Pull the live Arcus perp market facts right now — I want to see the hourly and annualized funding rates, open interest in both base and USD, mark vs oracle price spread, 24-hour volume, and the off-hours initial margin fraction for when the NYSE is closed.

## When to prefer this

Use this endpoint when you need live perpetual market data specifically from the Arcus venue (dYdX Labs on Robinhood Chain), particularly for tokenized-stock or index perps that are unique to that venue, or when you need the off-hours initial margin fraction that reflects NYSE session status. Prefer this over generic crypto derivatives endpoints when Arcus-specific venue data (mark vs oracle spread, Arcus funding) is needed for trading decisions or venue comparison.

## Known failure modes

- Missing or invalid PAYMENT-SIGNATURE header returns 402 Payment Required
- Expired or already-used EIP-3009 payment signature returns 402
- Insufficient USDC balance on Base mainnet causes payment failure
- Network congestion on Base mainnet may delay payment validation
- Arcus venue data outage may return stale or empty market data
- Malformed request without required GET method returns 400

## How this service works

Live perp market facts from Arcus (dYdX Labs on Robinhood Chain) for tokenized-stock, index, and crypto perps: hourly funding (+ annualized), open interest (base + USD), mark vs oracle price, 24h volume, and margin fractions including the off-hours initial margin (Arcus raises margin when the NYSE is closed). Perp-venue complement to stock-perp-facts.

## Output

Returns a JSON object with live Arcus perpetual market data including: hourly funding rate and its annualized equivalent, open interest in base asset and USD terms, current mark price and oracle price, 24-hour trading volume, standard margin fraction, and the elevated off-hours initial margin fraction that Arcus applies when the NYSE is closed — all for tokenized-stock, index, and crypto perps on Robinhood Chain.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "method"
   ],
   "properties": {
    "method": {
     "type": "string",
     "const": "GET"
    },
    "headers": {
     "type": "object",
     "required": [
      "PAYMENT-SIGNATURE"
     ],
     "properties": {
      "PAYMENT-SIGNATURE": {
       "type": "string",
       "description": "x402 EIP-3009 USDC payment signature (Base mainnet)"
      }
     }
    }
   }
  },
  "output": {
   "type": "object",
   "properties": {
    "action": {
     "enum": [
      "BUY",
      "SELL",
      "HOLD"
     ],
     "type": "string"
    },
    "signal": {
     "enum": [
      "BULLISH",
      "BEARISH",
      "NEUTRAL"
     ],
     "type": "string"
    },
    "btc_trend": {
     "enum": [
      "UP",
      "DOWN",
      "SIDEWAYS"
     ],
     "type": "string"
    },
    "reasoning": {
     "type": "string"
    },
    "confidence": {
     "type": "number",
     "maximum": 1,
     "minimum": 0
    },
    "fear_greed": {
     "type": "number",
     "maximum": 100,
     "minimum": 0
    },
    "polymarket_edge": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/arcus-perpetual-market-facts-api-023b242e/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.octodamus.com](https://www.zero.xyz/host/api.octodamus.com/llms.txt)