Swap API

Executable token swap calldata in one GET request. No API keys. No accounts. No SDK bloat.

https://api.swapapi.dev

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Quick Start

Swap 1 ETH for USDC on Ethereum:

curl "https://api.swapapi.dev/v1/swap/1?\
tokenIn=0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE&\
tokenOut=0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48&\
amount=1000000000000000000&\
sender=0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045"

That's it. The response contains everything you need to sign and broadcast.

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Example Response

{
  "success": true,
  "data": {
    "status": "Successful",
    "tokenFrom": {
      "address": "0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE",
      "symbol": "ETH",
      "name": "Ether",
      "decimals": 18
    },
    "tokenTo": {
      "address": "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
      "symbol": "USDC",
      "name": "USD Coin",
      "decimals": 6
    },
    "swapPrice": 2435.12,
    "priceImpact": 0.0003,
    "amountIn": "1000000000000000000",
    "expectedAmountOut": "2435120000",
    "minAmountOut": "2422947280",
    "tx": {
      "from": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
      "to": "0x011E52E4E40CF9498c79e329EBc29ed08c8B5abB",
      "data": "0x2646478b...",
      "value": "1000000000000000000",
      "gasPrice": 30000000000,
      "gas": "250000"
    }
  },
  "timestamp": "2026-03-12T00:00:00.000Z"
}

Field	Description
success	Boolean indicating request success
data.status	"Successful", "Partial", or "NoRoute"
data.tokenFrom/tokenTo	Token metadata (address, symbol, decimals)
data.swapPrice	Exchange rate
data.priceImpact	Slippage impact (0.001 = 0.1%)
data.expectedAmountOut	Estimated output in token's smallest unit
data.minAmountOut	Guaranteed minimum (respects your maxSlippage)
data.tx	Transaction object ready to sign and send

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API Reference

Endpoint: GET /v1/swap/{chainId}

Parameters:

Param	Required	Description
chainId	path	Chain ID (1=Ethereum, 8453=Base, 42161=Arbitrum, etc.)
tokenIn	query	Input token address. Use 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE for native ETH
tokenOut	query	Output token address
amount	query	Input amount in smallest unit (e.g., wei for ETH)
sender	query	Your wallet address (used to build the tx)
maxSlippage	query	Optional. 0-1 (default: 0.005 = 0.5%)

Response codes:

• 200 — Quote ready
• 400 — Invalid params or unsupported chain
• 429 — Rate limit exceeded (60/min per IP)
• 502 — Upstream service error

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More Curl Examples

Base (ETH → USDC)

curl "https://api.swapapi.dev/v1/swap/8453?\
tokenIn=0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE&\
tokenOut=0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913&\
amount=500000000000000000&\
sender=0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045"

Arbitrum (USDC → ETH with 1% slippage)

curl "https://api.swapapi.dev/v1/swap/42161?\
tokenIn=0xaf88d065e77c8cC2239327C5EDb3A432268e5831&\
tokenOut=0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE&\
amount=1000000000&\
sender=0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045&\
maxSlippage=0.01"

Ethereum Mainnet (DAI → USDC)

curl "https://api.swapapi.dev/v1/swap/1?\
tokenIn=0x6B175474E89094C44Da98b954EedeAC495271d0F&\
tokenOut=0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48&\
amount=1000000000000000000000&\
sender=0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045"

Polygon (MATIC → USDC)

curl "https://api.swapapi.dev/v1/swap/137?\
tokenIn=0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE&\
tokenOut=0x2791Bca1f2de4661ED88A30C99A7a9449Aa84174&\
amount=10000000000000000000&\
sender=0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045"

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Executing Swaps

The API gives you an unsigned transaction. Sign it and broadcast:

With Foundry cast

# 1. Set swap parameters
CHAIN_ID=8453
TOKEN_IN=0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE
TOKEN_OUT=0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913
AMOUNT=1000000000000000000
SENDER=0x...        # Your address
PRIVATE_KEY=0x...   # Your private key
RPC_URL=https://mainnet.base.org

# 2. Get swap quote
RESPONSE=$(curl -s "https://api.swapapi.dev/v1/swap/$CHAIN_ID?\
tokenIn=$TOKEN_IN&\
tokenOut=$TOKEN_OUT&\
amount=$AMOUNT&\
sender=$SENDER")

# 3. Parse the tx fields
TX_TO=$(echo "$RESPONSE" | jq -r '.data.tx.to')
TX_DATA=$(echo "$RESPONSE" | jq -r '.data.tx.data')
TX_VALUE=$(echo "$RESPONSE" | jq -r '.data.tx.value')
TX_GAS=$(echo "$RESPONSE" | jq -r '.data.tx.gas')

# 4. Sign and send
cast send \
  --rpc-url "$RPC_URL" \
  --private-key "$PRIVATE_KEY" \
  "$TX_TO" \
  --value "$TX_VALUE" \
  --gas-limit "$TX_GAS" \
  --data "$TX_DATA"

With viem

import { createWalletClient, http } from 'viem'
import { privateKeyToAccount } from 'viem/accounts'
import { base } from 'viem/chains'

const account = privateKeyToAccount('0x...')

const client = createWalletClient({
  account,
  chain: base,
  transport: http()
})

const response = await fetch(
  'https://api.swapapi.dev/v1/swap/8453?' +
  'tokenIn=0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE&' +
  'tokenOut=0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913&' +
  'amount=1000000000000000000&' +
  'sender=' + account.address
)

const { data } = await response.json()

const hash = await client.sendTransaction({
  to: data.tx.to,
  data: data.tx.data,
  value: BigInt(data.tx.value),
  gas: BigInt(data.tx.gas)
})

await client.waitForTransactionReceipt({ hash })

MCP Server

For AI agents, Claude Desktop, Cursor, Cline, and other MCP clients:

npx @swapapi/mcp

Or add to Claude Desktop config:

{
  "mcpServers": {
    "swapapi": {
      "command": "npx",
      "args": ["@swapapi/mcp"]
    }
  }
}

See mcp/README.md for full MCP documentation.

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OpenAPI Spec

See openapi.json for the full OpenAPI specification.

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Limits

• Rate limit: 60 requests/minute per IP
• No authentication required
• Free to use

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License

MIT