Swap API

What the Swap API MCP server does

The Swap API MCP server connects MCP clients to SwapAPI's token-swap quote endpoint. It prepares swap data for EVM chains from inputs such as the chain ID, input and output token addresses, amount in the token's smallest unit, and the sender's wallet address. An optional maxSlippage value controls the minimum acceptable output; the default is 0.5% when omitted.

The response includes token metadata, the exchange rate, price impact, input amount, expected output, minimum output, and an unsigned transaction. The transaction contains the destination address, calldata, native value, gas price, and gas limit. A client can pass those fields to a wallet or transaction library for signing and broadcast.

How it works

The underlying API uses GET /v1/swap/{chainId}. Ethereum, Base, Arbitrum, and Polygon are shown in the documentation through their chain IDs, while unsupported chains produce a client error. Native ETH is represented by the documented sentinel address; ERC-20 swaps use token contract addresses.

A successful response reports a status such as Successful, Partial, or NoRoute. The minAmountOut value reflects the requested slippage limit. The Swap API MCP server does not sign transactions or hold private keys: it supplies data for a separate execution step.

Setup and configuration

Install the MCP package with npm and register it as a local stdio server. The documented package is @swapapi/mcp:

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

The package is documented for Claude Desktop, Cursor, Cline, and other MCP clients. SwapAPI requires no API key, account, or authentication. The service is free to use, with a rate limit of 60 requests per minute per IP address.

Tools and capabilities

The available MCP capability is centered on requesting executable swap data from SwapAPI. Use it to:

• Prepare native-token or ERC-20 swaps on supported EVM chains.
• Set the input amount in wei or another smallest-unit representation.
• Supply the wallet address that will become the transaction sender.
• Apply a custom slippage limit between 0 and 1.
• Read quote, price-impact, minimum-output, and transaction fields before execution.

The resulting transaction can be used with tools such as Foundry cast or a viem wallet client, as illustrated by the project documentation.

Limitations and notes

The Swap API MCP server only prepares transaction data; it does not provide signing, private-key management, or broadcasting. Agents and applications must validate the token addresses, chain, amount, sender, and slippage before asking a wallet to sign.

Requests may fail with HTTP 400 for invalid parameters or unsupported chains, 429 after exceeding the per-IP limit, or 502 when the upstream service has an error. A response can also indicate that no route was found or that only a partial result is available. No API key is needed, but access remains subject to the stated rate limit and upstream availability.