CrossFin

The only way AI agents access Asian crypto markets.

CrossFin is a financial router for AI agents. It finds the cheapest path to move money across 7 exchanges (Bithumb, Upbit, Coinone, GoPax + Binance, OKX, Bybit), pays for APIs with crypto (x402 protocol), and gives agents real-time access to market data that's normally locked behind Korean-language interfaces and IP restrictions.

Live: crossfin.dev | Demo: live.crossfin.dev

Install in 30 seconds

Add this to your Claude Desktop config (claude_desktop_config.json):

{
  "mcpServers": {
    "crossfin": {
      "command": "npx",
      "args": ["-y", "crossfin-mcp"],
      "env": {
        "EVM_PRIVATE_KEY": "0x..."
      }
    }
  }
}

Restart Claude Desktop. Done. 16 tools available immediately.

No EVM key? Free tools (price lookup, fee comparison, kimchi premium) work without one. Paid tools ($0.01–$0.10 per call) require a Base wallet with USDC.

What can it do?

Ask your agent:

• "빗썸에서 바이낸스로 500만원 USDC 만들려면 가장 싼 방법이 뭐야?" → Routing engine evaluates 11 bridge coins across 7 exchanges, returns optimal path with fees
• "지금 김치 프리미엄 얼마야?" → Real-time price spread between Korean and global exchanges for 11 crypto pairs
• "삼성전자 외국인 매수 동향 알려줘" → Korean stock investor flow data (foreign/institutional/individual)
• "오늘 한국 시장 브리핑해줘" → Morning Brief bundle: kimchi premium + FX + KOSPI/KOSDAQ + stock momentum + headlines

For developers/agents:

• find_optimal_route — cheapest/fastest/balanced path across Bithumb, Upbit, Coinone, GoPax, Binance, OKX, Bybit using 11 bridge coins (BTC, ETH, XRP, SOL, DOGE, ADA, DOT, LINK, AVAX, TRX, KAIA)
• get_kimchi_premium — real-time Korean vs. global price spread
• compare_exchange_prices — live price comparison across Korean exchanges
• call_paid_service — call any of 35 paid APIs with automatic x402 USDC payment

Why CrossFin?

Korean exchanges are a walled garden. Korean-language APIs, IP restrictions, real-name bank account requirements (실명확인 계좌제), and no English documentation. AI agents can't access them — unless they go through CrossFin.

Prices differ across exchanges. The same BTC can be 2-3% more expensive on Korean exchanges (kimchi premium). CrossFin's routing engine finds the cheapest bridge coin and path, factoring in trading fees, withdrawal fees, slippage, and transfer time.

x402 native. No API keys, no subscriptions, no invoices. Agents pay per call with USDC on Base. $0.01 for an FX rate, $0.10 for a full routing analysis.

Routing Engine

The core product. Given a source (exchange + currency) and destination, CrossFin evaluates all possible paths:

Input:  bithumb:KRW → binance:USDC, ₩5,000,000
Output: Buy AVAX on Bithumb → Transfer to Binance → Sell for USDC
        Cost: 0.07% (₩3,500) | Time: ~3 min | Output: $3,452 USDC

        Alternatives:
        BTC  → 0.33% | ~21 min | $3,443
        DOT  → 0.38% | ~6 min  | $3,441

Considers: trading fees (0.10–0.25%), withdrawal fees (fixed per coin), orderbook slippage, transfer time, kimchi premium direction.

Supports bidirectional routing: Korea → Global and Global → Korea.

Free preview: POST /api/acp/quote (ACP compatible) Full route: GET /api/premium/route/find ($0.10 via x402)

MCP Tools (16 total)

35 Paid APIs

All paid via x402 (USDC on Base). No API key needed.

Payment (x402)

No API keys. No subscriptions. Pay per call with USDC on Base.

import { x402Client, wrapFetchWithPayment } from '@x402/fetch'
import { registerExactEvmScheme } from '@x402/evm/exact/client'
import { privateKeyToAccount } from 'viem/accounts'

const signer = privateKeyToAccount(process.env.EVM_PRIVATE_KEY)
const client = new x402Client()
registerExactEvmScheme(client, { signer })

const paidFetch = wrapFetchWithPayment(fetch, client)
const res = await paidFetch('https://crossfin.dev/api/premium/arbitrage/kimchi')
console.log(await res.json())

import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

client = x402ClientSync()
account = Account.from_key(os.environ['EVM_PRIVATE_KEY'])
register_exact_evm_client(client, EthAccountSigner(account))

with x402_requests(client) as session:
    r = session.get('https://crossfin.dev/api/premium/arbitrage/kimchi')
    print(r.json())

Tech Stack

Cloudflare Workers + Hono, D1 (SQLite), x402 protocol, USDC on Base, MCP SDK, React + Vite (dashboard)

Project Structure

apps/
  api/          Cloudflare Workers API
  mcp-server/   MCP Server (16 tools, npm: crossfin-mcp)
  web/          Gateway Dashboard (crossfin.dev)
  live/         Live Demo (live.crossfin.dev)
  docs/         Documentation (docs.crossfin.dev)

Links

• Dashboard — Gateway UI
• Live Demo — Real-time routing demo
• Agent Guide — Structured JSON for agents
• OpenAPI Spec — Machine-readable API spec
• Docs — Developer documentation
• npm: crossfin-mcp — MCP server package

Built with AI

CrossFin was built entirely through AI collaboration by a non-developer in 3 weeks. Zero prior coding experience. This project is proof that AI agents can build production software — and CrossFin is the infrastructure for that future.