MetaMask MCP

import type { Config } from "@wagmi/core"; import type { FastMCP } from "fastmcp"; import { simulateContract, writeContract } from "@wagmi/core"; import { Abi, Address } from "abitype/zod"; import { TransactionExecutionError } from "viem"; import { z } from "zod"; import { JSONStringify } from "../utils/json-stringify"; export function registerWriteContractTools(server: FastMCP, wagmiConfig: Config): void { server.addTool({ name: "write-contract", description: "Execute a write function on a contract.", parameters: z.object({ abi: Abi.describe("The contract's ABI."), address: Address.describe("The contract's address."), functionName: z.string().describe("Function to call on the contract."), args: z.unknown().array().optional().describe("Arguments to pass when calling the contract."), value: z.coerce.bigint().optional().describe("Value in wei sent with this transaction."), maxFeePerGas: z.coerce.bigint().optional().describe("Total fee per gas in wei, inclusive of maxPriorityFeePerGas."), maxPriorityFeePerGas: z.coerce.bigint().optional().describe("Max priority fee per gas in wei."), chainId: z.coerce.number().optional().describe("Chain ID to validate against before sending transaction."), }), execute: async (args) => { try { const { request } = await simulateContract(wagmiConfig, args); const result = await writeContract(wagmiConfig, request); return { content: [ { type: "text", text: JSONStringify({ hash: result, }), }, ], }; } catch (error) { if (error instanceof TransactionExecutionError) { return { content: [ { type: "text", text: error.cause.message, }, ], }; } return { content: [ { type: "text", text: (error as Error).message, }, ], }; } }, }); };