API Reference

Base URL: https://api.swapapi.dev

All responses use a consistent envelope format with success, data (or error), and timestamp fields.

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GET /v1/swap/{chainId}

Returns a swap quote with executable transaction data. This is the core endpoint.

Path parameters

Param	Type	Required	Description
chainId	integer	yes	EVM chain ID. See Supported Chains.

Query parameters

Param	Type	Required	Default	Description
tokenIn	address	yes	—	Token to sell. Use 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE for native ETH/gas token.
tokenOut	address	yes	—	Token to buy.
amount	string	yes	—	Amount to swap in the token's smallest unit (wei for ETH, 6-decimal units for USDC, etc). Must be a numeric string.
sender	address	yes	—	Address that will execute the swap transaction.
maxSlippage	number	no	0.005	Maximum allowed slippage as a decimal. 0.005 = 0.5%. Range: 0 to 1.

Address format

All address parameters must be a valid 0x-prefixed hex address: 0x followed by exactly 40 hex characters.

Example request

curl "https://api.swapapi.dev/v1/swap/8453?\
tokenIn=0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE&\
tokenOut=0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913&\
amount=1000000000000000000&\
sender=0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045&\
maxSlippage=0.01"

Success response (200)

{
  "success": true,
  "data": {
    "status": "Successful",
    "tokenFrom": {
      "address": "0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE",
      "symbol": "ETH",
      "name": "Ether",
      "decimals": 18
    },
    "tokenTo": {
      "address": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "symbol": "USDC",
      "name": "USD Coin",
      "decimals": 6
    },
    "swapPrice": 2435.12,
    "priceImpact": 0.0003,
    "amountIn": "1000000000000000000",
    "expectedAmountOut": "2435120000",
    "tx": {
      "from": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
      "to": "0x011E52E4E40CF9498c79e329EBc29ed08c8B5abB",
      "data": "0x2646478b...",
      "value": "1000000000000000000",
      "gasPrice": 30000000000,
      "gas": "250000"
    }
  },
  "timestamp": "2026-03-12T00:00:00.000Z"
}

Response fields

Field	Type	Description
success	boolean	Always true for successful responses.
data.status	string	Quote status: "Successful" (full swap available), "Partial" (only part of the amount can be swapped), or "NoRoute" (no viable route found).
data.tokenFrom	object	Input token info: address, symbol, name, decimals.
data.tokenTo	object	Output token info: address, symbol, name, decimals.
data.swapPrice	number	Exchange rate — units of output token per one input token.
data.priceImpact	number	Estimated price impact as a decimal (0.001 = 0.1%).
data.amountIn	string	Input amount in smallest token unit (echoed from request).
data.expectedAmountOut	string	Guaranteed minimum output amount in the output token's smallest unit.
data.tx.from	string	Sender address (echoed from request).
data.tx.to	string	Router contract address to send the transaction to.
data.tx.data	string	Encoded calldata for the swap.
data.tx.value	string	Native token value to include. Non-zero when selling native ETH.
data.tx.gasPrice	number	Suggested gas price in wei.
data.tx.gas	string	Estimated gas limit.
timestamp	string	ISO 8601 timestamp.

Error responses

All errors follow this format:

{
  "success": false,
  "error": {
    "code": "ERROR_CODE",
    "message": "Human-readable description",
    "details": {}
  },
  "timestamp": "2026-03-12T00:00:00.000Z"
}

400 — Validation Error

Returned when request parameters fail validation (missing required params, invalid address format, etc).

{
  "success": false,
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid request parameters",
    "details": {
      "issues": [
        {
          "code": "invalid_string",
          "message": "Invalid",
          "path": ["tokenIn"]
        }
      ]
    }
  },
  "timestamp": "2026-03-12T00:00:00.000Z"
}

400 — Unsupported Chain

Returned when the chain ID is not supported.

{
  "success": false,
  "error": {
    "code": "UNSUPPORTED_CHAIN",
    "message": "Chain 999 is not supported",
    "details": {
      "chainId": 999
    }
  },
  "timestamp": "2026-03-12T00:00:00.000Z"
}

400 / 502 — Upstream Error

Returned when the routing engine encounters an error. 400 for client-side issues, 502 for upstream failures.

{
  "success": false,
  "error": {
    "code": "UPSTREAM_ERROR",
    "message": "Routing engine returned an error",
    "details": {
      "upstream": "No route found for the given pair"
    }
  },
  "timestamp": "2026-03-12T00:00:00.000Z"
}

429 — Rate Limited

{
  "success": false,
  "error": {
    "code": "RATE_LIMIT",
    "message": "Rate limit exceeded"
  },
  "timestamp": "2026-03-12T00:00:00.000Z"
}

500 — Internal Error

{
  "success": false,
  "error": {
    "code": "INTERNAL_ERROR",
    "message": "Internal server error"
  },
  "timestamp": "2026-03-12T00:00:00.000Z"
}

---

GET /health

Health check endpoint. Not rate limited.

Example request

curl "https://api.swapapi.dev/health"

Response (200)

{
  "success": true,
  "data": {
    "status": "ok"
  },
  "timestamp": "2026-03-12T00:00:00.000Z"
}

---

GET /openapi.json

Returns the full OpenAPI 3.1.0 specification for the API. This is machine-readable and can be consumed directly by:

• Swagger UI / Redoc for interactive documentation
• OpenAI GPT Actions / function calling
• LangChain API tools
• Any OpenAPI-compatible code generator

curl "https://api.swapapi.dev/openapi.json"

A Swagger UI is also available at /docs.

---

GET /llms.txt

Returns a plain-text description of the API designed for LLM tool discovery. When an AI agent fetches this file, it gets everything it needs to construct valid API calls — endpoint URL, parameters, and examples — in a format optimized for language model consumption.

curl "https://api.swapapi.dev/llms.txt"

This follows the llms.txt convention for making APIs discoverable by AI agents.

---

Quick reference

Endpoint: GET https://api.swapapi.dev/v1/swap/{chainId}
Required params: tokenIn, tokenOut, amount, sender
Optional params: maxSlippage (default: 0.005)
Auth: None
Rate limit: 60 req/min per IP