DEX Swap Quotes API

Best swap quotes across Uniswap, SushiSwap, Aerodrome -- price impact, route, slippage. Pre-trade essential. Pay-per-call via x402 (USDC on Base L2) -- no API key, no signup, no rate-limit wall.

Part of the klymax402 marketplace -- 100 x402 micropayment APIs for AI agents, one wallet, USDC on Base.

Quickstart -- MCP

Add to your MCP client config (Claude Desktop, Cursor, ElizaOS, etc.):

config.json

{
  "mcpServers": {
    "dex-quotes": {
      "url": "https://dex-quotes.api.klymax402.com/mcp"
    }
  }
}

Quickstart -- HTTP (x402)

Terminal

curl "https://dex-quotes.api.klymax402.com/api/quote?tokenIn=...&tokenOut=...&amount=..."
# -> 402 Payment Required, with an x402 payment challenge in the response body

Any x402-aware client (@x402/fetch, x402-agent-tools, ATXP) handles the 402 -> sign -> retry cycle automatically.

Tools

Tool	Method	Path	Price	Description
`dex_get_swap_quote`	GET	`/api/quote`	$0.012	Get the best swap quote across multiple DEXes
`dex_get_swap_quote`	POST	`/api/quote`	$0.012	Get the best swap quote across multiple DEXes (POST variant)

`dex_get_swap_quote`

Use this when you need a swap quote before trading tokens on-chain. Returns the best price across multiple DEXes in JSON.

Parameters

Name	Type	Required	Description
`tokenIn`	string	yes	Contract address of input token (e.g. 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 for USDC on Base)
`tokenOut`	string	yes	Contract address of output token (e.g. 0x4200000000000000000000000000000000000006 for WETH on Base)
`amount`	string	yes	Amount of input token in raw units (wei/smallest unit, e.g. 1000000 for 1 USDC)
`chain`	string	no	Blockchain network: base or ethereum (default: base)

Returns

bestDex -- which DEX offers the best rate (Uniswap, SushiSwap, Aerodrome)
amountOut -- expected output token amount
priceImpact -- percentage price impact of the trade
minimumReceived -- minimum output after slippage tolerance
route -- swap path (e.g. USDC -> WETH -> TOKEN)
gasEstimateUsd -- estimated gas cost in USD

Example response:

config.json

{"bestDex":"Uniswap V3","amountOut":"0.3215","priceImpact":"0.12%","minimumReceived":"0.3183","route":["USDC","WETH"],"gasEstimateUsd":0.04}

When to use: executing any token swap to find the best rate and estimate slippage. Essential for trade sizing and DEX comparison.

Not for: gas estimation only (use gas_get_current_price), yield opportunities (use defi_find_best_yields), wallet balance (use wallet_get_portfolio).

`dex_get_swap_quote`

Use this when you need a swap quote before trading tokens on-chain. Returns the best price across multiple DEXes in JSON. POST variant of dex_get_swap_quote -- same params passed as JSON body instead of query string.

Parameters

Name	Type	Required	Description
`tokenIn`	string	yes	Contract address of input token (e.g. 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 for USDC on Base)
`tokenOut`	string	yes	Contract address of output token (e.g. 0x4200000000000000000000000000000000000006 for WETH on Base)
`amount`	string	yes	Amount of input token in raw units (wei/smallest unit, e.g. 1000000 for 1 USDC)
`chain`	string	no	Blockchain network: base or ethereum (default: base)

Returns

bestDex -- which DEX offers the best rate (Uniswap, SushiSwap, Aerodrome)
amountOut -- expected output token amount
priceImpact -- percentage price impact of the trade
minimumReceived -- minimum output after slippage tolerance
route -- swap path (e.g. USDC -> WETH -> TOKEN)
gasEstimateUsd -- estimated gas cost in USD

Example response:

config.json

{"bestDex":"Uniswap V3","amountOut":"0.3215","priceImpact":"0.12%","minimumReceived":"0.3183","route":["USDC","WETH"],"gasEstimateUsd":0.04}

When to use: executing any token swap to find the best rate and estimate slippage. Essential for trade sizing and DEX comparison.

Not for: gas estimation only (use gas_get_current_price), yield opportunities (use defi_find_best_yields), wallet balance (use wallet_get_portfolio).

Example agent prompts

"A swap quote before trading tokens on-chain"
"A swap quote before trading tokens on-chain"

Payment

Protocol: x402 -- HTTP-native pay-per-call, no signup, no API key
Network: Base L2 (eip155:8453)
Asset: USDC
Facilitator: Coinbase CDP (primary), PayAI (fallback)
Also reachable via ATXP (OAuth-wrapped x402, RFC 9728 protected-resource metadata)

Part of klymax402

100 x402 micropayment APIs for AI agents -- one wallet, USDC on Base, zero signup.

Catalog: https://klymax402.com/llms.txt
Full API reference: https://klymax402.com/llms-full.txt
Live stats: https://klymax402.com/stats

License

MIT