Swap

The Swap API converts one token into another — same-chain (e.g. USDC → USDT on Polygon, via Rach’s on-chain FiatSwapV2 proxy) or cross-chain (e.g. Polygon → BSC, via a bridge). Quote first, then execute. Authenticate with your Payments API key (X-API-Key).

Base URL: https://api.rach.finance/api/v1/ · Auth: X-API-Key (quote is public)

Amounts are in base units

amount_in and every amount in the response are in base units, not whole tokens. amount_in=100 on USDC means 100 base units = 0.0001 USDC, not 100 USDC.Use amount to pass a human figure instead — amount=100 means 100 USDC. Pass one or the other, never both.Responses are always base units. Divide by the token’s decimals to display them: USDC/USDT are 6 on most chains but 18 on BSC; native coins (ETH, BNB, POL, AVAX, CELO) are 18.

1. Get a quote

GET /swap/quote is public — no key required.

# amount = human units (100 USDC). Use amount_in only for pre-converted base units.
curl "https://api.rach.finance/api/v1/swap/quote?from_chain=POL&to_chain=POL&from_token=USDC&to_token=USDT&amount=100"

Response

{
  "from_chain": "POL",
  "to_chain": "POL",
  "from_token": "0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359",
  "to_token": "0xc2132D05D31c914a87C6611C10748AEb04B58e8F",
  "from_amount": "100000000",
  "to_amount_expected": "98046740",
  "to_amount_min": "97556410",
  "platform_fee": "300000",
  "estimated_seconds": 30,
  "expires_at": 1755168000
}

Both tokens come back as resolved contract addresses, and all amounts are base units — here 6-decimal USDC, so 98046740 is 98.04674 USDT. The platform fee is 0.30%. to_amount_min reflects slippage protection — the swap reverts if output would fall below it.

Routing is automatic

You do not choose a venue. Rach picks it from the chains and tokens you pass:

Your request	Route
Same chain, on POL or BSC	Rach’s own on-chain FiatSwapV2 contract
Same chain, any other chain	LiFi aggregator
Different chains	LiFi bridge

If our contract cannot serve a same-chain pair (no pool or liquidity), the quote falls back to LiFi automatically. Nothing is broadcast during quoting, so the fallback is free.

Execution currently starts from a POL or BSC wallet only. A request whose from_chain is anything else is rejected up front with a clear error — quotes still work for any pair.

2. Execute the swap

Run the swap for a customer wallet. Pass amount_out_min to protect against slippage — the quote’s to_amount_min is exactly what you want here.

amount_out_min must use the same unit as the amount field you sent. Send amount_in (base units) and amount_out_min is read as base units; send amount (human) and it is read as human. Mixing them silently sets the wrong slippage floor.The quote returns base units, so feeding a quote straight into execution means using amount_in + to_amount_min together — as below.

# Base units throughout, taken directly from the quote response.
curl https://api.rach.finance/api/v1/swap/customer/cust_001 \
  -H "X-API-Key: $RACH_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "from_chain": "POL",
    "to_chain": "POL",
    "from_token": "USDC",
    "to_token": "USDT",
    "amount_in": "100000000",
    "amount_out_min": "97556410"
  }'

// Quote first, then pass its base-unit figures straight through.
const q = await (await fetch(
  "https://api.rach.finance/api/v1/swap/quote?from_chain=POL&to_chain=POL" +
  "&from_token=USDC&to_token=USDT&amount=100")).json();

const swap = await (await fetch("https://api.rach.finance/api/v1/swap/customer/cust_001", {
  method: "POST",
  headers: { "X-API-Key": process.env.RACH_KEY, "Content-Type": "application/json" },
  body: JSON.stringify({
    from_chain: "POL", to_chain: "POL",
    from_token: "USDC", to_token: "USDT",
    amount_in: q.from_amount,          // base units
    amount_out_min: q.to_amount_min,   // base units — same unit as amount_in
  }),
})).json();

Response

{ "tx_hash": "0x9f8e...", "status": "pending" }

status is pending when the transaction is broadcast — not when the swap has settled. Rach confirms it in the background; poll history for the final confirmed or failed. Cross-chain swaps can take several minutes to complete on the destination chain.

Re-quote if a quote is more than a few seconds old. If the live route can no longer deliver your amount_out_min, execution stops before anything is broadcast and returns an error telling you to re-quote — your customer’s funds are never at risk from a stale quote.

3. Track history

curl https://api.rach.finance/api/v1/swap/customer/cust_001/history \
  -H "X-API-Key: $RACH_KEY"

Same-chain swaps on Polygon and BSC route through Rach’s FiatSwapV2 proxy (0.30% platform fee, applied on-chain). Cross-chain swaps bridge via an aggregator and take longer — estimated_seconds reflects the route.

See the Swap endpoints in the Payments API Reference.

Get Started

Core Products

Monitoring & Webhooks

Amounts are in base units

1. Get a quote

Routing is automatic

2. Execute the swap

3. Track history

​Amounts are in base units

​1. Get a quote

​Routing is automatic

​2. Execute the swap

​3. Track history

Amounts are in base units

1. Get a quote

Routing is automatic

2. Execute the swap

3. Track history