# HARS-Zero Signal API – Live FX Rate Lookup

> HARS-Zero Signal API – Live FX Rate Lookup is a paid API for AI agents from hars.cryptotavern.xyz, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).

Returns a live foreign exchange rate for a currency pair, including a 24-hour sparkline, confidence score, and inverse rate, paid per call in USDC via x402.

## Facts

- Endpoint: GET https://hars.cryptotavern.xyz/paid/fx
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hars-zero-signal-api-live-fx-rate-lookup-0c7ebfa8
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_fO4JZdUyEVvsRrNs-rx2n

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 hars-zero-signal-api-live-fx-rate-lookup-0c7ebfa8
```

Example prompt: What's the live exchange rate from USD to EUR right now, and can you show me how the rate has trended over the last 24 hours?

## When to prefer this

Choose this endpoint when your agent needs a live, pay-per-call FX rate with no API key setup, especially in high-volume loops where sub-cent per-call pricing matters. It is ideal for autonomous agents that already use x402/USDC micropayments on Base or Solana, and need a 24-hour sparkline or confidence score alongside the raw rate rather than a bare number from a free tier.

## Known failure modes

- Unsupported or malformed currency codes return an error or empty rate
- Payment failure via x402 (insufficient USDC balance or unsupported chain) results in a 402 response with no data
- Stale or low-confidence rates may be returned during market closure or data source outages, indicated by a low confidence score
- Missing required 'from' or 'to' parameters cause a validation error

## How this service works

Utility API for AI agents — fetch URLs, extract structured HTML,
summarize text, get live FX rates, and geocode addresses. Pay per call
in USDC on Base or Solana via x402. No API keys, no subscriptions.
Sub-cent pricing optimized for high-volume agent loops.

## Output

Returns a JSON object with the from/to currency codes, the live exchange rate as a float, the inverse rate, an RFC3339 timestamp for the rate, an optional 24-hour sparkline array of prices, a confidence score (0–1), a list of risk factors, evidence URLs (e.g. Polymarket reference links), the converted amount if an input amount was provided, and an optional next_best_action suggestion for follow-up calls.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "as_of",
  "from",
  "to",
  "rate"
 ],
 "properties": {
  "to": {
   "type": "string"
  },
  "from": {
   "type": "string"
  },
  "rate": {
   "type": "number"
  },
  "as_of": {
   "type": "string",
   "format": "date-time",
   "description": "RFC3339 timestamp"
  },
  "risks": {
   "type": "array",
   "items": {
    "type": "string"
   }
  },
  "amount": {
   "type": "number"
  },
  "source": {
   "type": "string"
  },
  "product": {
   "type": "string"
  },
  "evidence": {
   "type": "array",
   "items": {
    "type": "string",
    "format": "uri"
   },
   "description": "Polymarket order book / event / reference URLs"
  },
  "sparkline": {
   "type": "array",
   "items": {
    "type": "number"
   }
  },
  "confidence": {
   "type": "number",
   "maximum": 1,
   "minimum": 0,
   "description": "Model confidence 0.0-1.0"
  },
  "market_ids": {
   "type": "array",
   "items": {
    "type": "string"
   },
   "description": "Polymarket slugs or ids referenced in this response"
  },
  "inverse_rate": {
   "type": "number"
  },
  "converted_amount": {
   "type": "number"
  },
  "next_best_action": {
   "type": "object",
   "properties": {
    "why": {
     "type": "string"
    },
    "endpoint": {
     "type": "string"
    },
    "price_usd": {
     "type": "number"
    },
    "product_id": {
     "type": "string"
    }
   }
  }
 },
 "description": "Currency pair -> live FX rate + 24h sparkline."
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "as_of",
  "from",
  "to",
  "rate"
 ],
 "properties": {
  "to": {
   "type": "string"
  },
  "from": {
   "type": "string"
  },
  "rate": {
   "type": "number"
  },
  "as_of": {
   "type": "string",
   "format": "date-time",
   "description": "RFC3339 timestamp"
  },
  "risks": {
   "type": "array",
   "items": {
    "type": "string"
   }
  },
  "amount": {
   "type": "number"
  },
  "source": {
   "type": "string"
  },
  "product": {
   "type": "string"
  },
  "evidence": {
   "type": "array",
   "items": {
    "type": "string",
    "format": "uri"
   },
   "description": "Polymarket order book / event / reference URLs"
  },
  "sparkline": {
   "type": "array",
   "items": {
    "type": "number"
   }
  },
  "confidence": {
   "type": "number",
   "maximum": 1,
   "minimum": 0,
   "description": "Model confidence 0.0-1.0"
  },
  "market_ids": {
   "type": "array",
   "items": {
    "type": "string"
   },
   "description": "Polymarket slugs or ids referenced in this response"
  },
  "inverse_rate": {
   "type": "number"
  },
  "converted_amount": {
   "type": "number"
  },
  "next_best_action": {
   "type": "object",
   "properties": {
    "why": {
     "type": "string"
    },
    "endpoint": {
     "type": "string"
    },
    "price_usd": {
     "type": "number"
    },
    "product_id": {
     "type": "string"
    }
   }
  }
 },
 "description": "Currency pair -> live FX rate + 24h sparkline."
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hars-zero-signal-api-live-fx-rate-lookup-0c7ebfa8/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from hars.cryptotavern.xyz](https://www.zero.xyz/host/hars.cryptotavern.xyz/llms.txt)