infura-mcp-server
Version:
Model Context Protocol (MCP) server providing comprehensive read-only Ethereum blockchain access through Infura's infrastructure. Connect Claude Desktop, VS Code, and Cursor to 29 secure Ethereum JSON-RPC tools across 30+ networks including Ethereum, Poly
109 lines (105 loc) • 4.57 kB
JavaScript
/**
* @fileoverview Tool for executing read-only smart contract calls via Infura JSON-RPC API.
* @module tools/eth-call
*
* This tool executes a message call to a smart contract without creating a transaction
* on the blockchain. It is commonly used to read data from contracts, such as querying
* ERC-20 token balances, fetching NFT metadata, or calling any view/pure function.
*
* The call is executed against the "latest" block state.
*
* @see {@link https://docs.infura.io/api/networks/ethereum/json-rpc-methods/eth_call|Infura eth_call docs}
* @see {@link https://ethereum.org/en/developers/docs/apis/json-rpc/#eth_call|Ethereum JSON-RPC spec}
*
* @example
* // Query ERC-20 token balance (balanceOf function selector: 0x70a08231)
* const result = await eth_call({
* to: "0xdAC17F958D2ee523a2206206994597C13D831ec7", // USDT contract
* data: "0x70a08231000000000000000000000000d8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
* network: "mainnet"
* });
* // Returns: "0x0000000000000000000000000000000000000000000000000000000005f5e100"
*
* @example
* // Call a contract on Sepolia testnet
* const result = await eth_call({
* to: "0x1234567890123456789012345678901234567890",
* data: "0x06fdde03", // name() function selector
* network: "sepolia"
* });
*/
import { callInfura } from "../lib/infura-client.js";
import { validateAddress, isValidHexString, ValidationError } from "../lib/validators.js";
/**
* Executes the eth_call JSON-RPC method to perform a read-only contract call.
*
* @param {Object} args - The function arguments.
* @param {string} args.to - Target contract address (0x-prefixed, 40 hex characters).
* @param {string} args.data - ABI-encoded function call data (0x-prefixed hex string).
* @param {string} [args.network="mainnet"] - Target Ethereum network (e.g., "mainnet", "sepolia", "holesky").
* @returns {Promise<string>} ABI-encoded return value as a hexadecimal string.
* @throws {ValidationError} If the "to" address format is invalid.
* @throws {ValidationError} If the "data" is not a valid hex string starting with 0x.
* @throws {McpError} If the contract execution reverts or Infura API fails.
*/
const executeFunction = async ({ to, data, network = "mainnet" }) => {
validateAddress(to, 'to');
if (!isValidHexString(data)) {
throw new ValidationError('Invalid data format. Expected hex string starting with 0x.', 'data');
}
const params = [
{
to,
data,
},
"latest",
];
return callInfura("eth_call", params, network);
};
/**
* Tool configuration for making Ethereum calls using Infura.
* @type {Object}
*/
const apiTool = {
function: executeFunction,
definition: {
type: "function",
function: {
name: "eth_call",
description:
"Execute a read-only smart contract call without creating a transaction.\n\nArgs:\n - to (string): Contract address to call (20-byte hex, e.g., '0x...').\n - data (string): ABI-encoded function call data (hex string starting with 0x).\n - network (string, optional): Ethereum network to query. Defaults to 'mainnet'.\n\nReturns:\n - Hexadecimal string containing the return value of the executed contract method.\n\nExamples:\n - \"Read ERC20 balance\": { \"to\": \"0xdAC17F958D2ee523a2206206994597C13D831ec7\", \"data\": \"0x70a08231000000000000000000000000...\" }\n - \"Query on Sepolia\": { \"to\": \"0x...\", \"data\": \"0x...\", \"network\": \"sepolia\" }\n\nErrors:\n - InvalidParams: When 'to' address or 'data' format is invalid.\n - InternalError: When contract execution reverts or Infura API fails.",
parameters: {
type: "object",
properties: {
to: {
type: "string",
description: "The address of the contract to call.",
},
data: {
type: "string",
description: "The data to send with the call.",
},
network: {
type: "string",
description: "The Ethereum network to query, e.g., 'mainnet' or 'sepolia'.",
default: "mainnet",
},
response_format: {
type: "string",
enum: ["json", "markdown"],
description: "Output format: 'json' for structured data, 'markdown' for human-readable.",
default: "json",
},
},
required: ["to", "data"],
},
annotations: {
readOnlyHint: true,
destructiveHint: false,
idempotentHint: true,
openWorldHint: true,
},
},
},
};
export { apiTool };