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.):

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

Quickstart -- HTTP (x402)

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:

{"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:

{"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