DEX Swap Quotes API

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