iso.currency

Look up an ISO 4217 currency. Pass code (alphabetic like USD, or 3-digit numeric like 840) for the canonical record, or country to find the currency/currencies a country uses. Returns the alphabetic + numeric code, English name, minor unit (decimal places — e.g. JPY 0, USD 2, BHD 3), and the countries using it. Bundled authoritative ISO 4217 data — the currency-code + decimal-places ground truth an LLM gets wrong on less-common currencies.

Overview

The currency API is a pay-per-call iso endpoint built for AI agents and autonomous software. Look up an ISO 4217 currency.

There is no signup and no API key. An agent (or any HTTP client) hits the endpoint, receives an x402 "402 Payment Required" challenge, signs a sub-cent USDC payment on Base or Solana, and retries — the data comes back on the paid request. That makes it a drop-in currency data source for an agent tool-use loop, an MCP host, or a backend that needs iso data on demand without onboarding to yet another vendor portal.

Use cases

• Give an AI agent live currency lookups as a tool, with no API key to provision or rotate — the agent pays per call from a wallet you fund.
• Enrich records in a data pipeline with iso data, paying only for the calls you actually make instead of a monthly seat.
• Ground LLM answers in authoritative iso data to cut hallucination, then optionally request a signed response for verifiability.
• Prototype against the live currency API in minutes using the free trial call, then flip to per-call x402 payment for production with no code change.

Parameters

Code samples

# 1. Probe with no auth → 402 envelope with PaymentRequirements
curl -sS 'https://2s.io/api/iso/currency?code=xx&country=xx'

# 2. Sign + retry with PAYMENT-SIGNATURE:
curl -sS 'https://2s.io/api/iso/currency?code=xx&country=xx' \
  -H 'PAYMENT-SIGNATURE: <base64-json-payload>'

# Or use the canonical runner (handles probe → sign → retry):
#   EVM_PRIVATE_KEY=0x... node --env-file=.env.local \
#     --experimental-strip-types scripts/x402-pay.ts \
#     'https://2s.io/api/iso/currency?code=xx&country=xx'

import { TwoS } from '@2sio/sdk'

const client = new TwoS({
  privateKey: process.env.EVM_PRIVATE_KEY as `0x${string}`,
})

const result = await client.iso.currency({
  "code": "xx",
  "country": "xx"
})

console.log('endpoint:', result.endpoint)
console.log('cost:', result.costUsd, 'USDC')
console.log('tx:', result.settlement?.txHash)
console.log('data:', result.data)

import os
from twosio import TwoS

client = TwoS(private_key=os.environ["EVM_PRIVATE_KEY"])

result = client.iso.currency(code="xx", country="xx")

print("endpoint:", result.endpoint)
print("cost:", result.cost_usd, "USDC")
print("tx:", (result.settlement or {}).get("tx_hash"))
print("data:", result.data)

// 1. Add @2sio/mcp to your MCP host config (Claude Desktop example below).
//    EVM_PRIVATE_KEY funds x402 payments per call.

// claude_desktop_config.json
{
  "mcpServers": {
    "2sio": {
      "command": "npx",
      "args": ["-y", "@2sio/mcp"],
      "env": { "EVM_PRIVATE_KEY": "0x..." }
    }
  }
}

// 2. Once the server is running, agents call this tool via standard MCP:

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "iso.currency",
    "arguments": {
      "code": "xx",
      "country": "xx"
    }
  }
}

Response

{
  "query": {
    "code": "example",
    "country": "example"
  },
  "found": false,
  "currencies": [
    {
      "code": "example",
      "name": "example",
      "numeric": "example",
      "minorUnit": 1,
      "countries": [
        "example"
      ]
    }
  ],
  "source": {
    "provider": "example",
    "url": "example",
    "license": "example"
  }
}

FAQ

Do I need an API key to use the currency API?

No. iso.currency is x402-native — there is no signup and no API key. Your client makes the call, receives a 402 with payment requirements, signs a USDC payment, and retries. Funds come from a wallet you control.

How much does the currency API cost?

$0.0012 USDC per call, charged per request. There are no monthly fees, seats, or minimums — you pay only for the calls you make.

Can I try the currency API for free first?

Yes. Add ?trial=1 (or the header X-2s-Trial: 1) to get a free real call per endpoint per hour, so you can verify the response shape before wiring payment.

Which networks and tokens are supported?

USDC on Base (via EIP-3009 transferWithAuthorization) or Solana (SPL transfer), using the open x402 payment protocol.

How do I call iso.currency from an AI agent or MCP host?

Use @2sio/sdk (TypeScript), 2sio (Python), or the @2sio/mcp server for any MCP host — each handles the probe → sign → retry loop for you. See the code samples on this page.

Discovery

• /api/directory — full catalog of every endpoint
• /openapi.json — OpenAPI 3.1 spec (per-op x-payment-info, x402Payment security)
• /.well-known/x402 — machine-readable service descriptor for x402-aware crawlers
• /.well-known/mcp/server-card.json — MCP SEP-1649 server card
• /llms.txt — plain-text manifest for LLM ingestion