Base MCP Server

import { ActionProvider, CreateAction, EvmWalletProvider, type Network, } from '@coinbase/agentkit'; import { base } from 'viem/chains'; import type { z } from 'zod'; import { FarcasterUsernameSchema } from './schemas.js'; import type { NeynarUserResponse } from './types.js'; export class FarcasterActionProvider extends ActionProvider<EvmWalletProvider> { constructor() { super('farcaster', []); } @CreateAction({ name: 'farcaster_username', description: 'Resolve a Farcaster username to an Ethereum address', schema: FarcasterUsernameSchema, }) async farcasterUsername( walletProvider: EvmWalletProvider, args: z.infer<typeof FarcasterUsernameSchema>, ) { const { username } = args; // Get Neynar API key from environment variables const neynarApiKey = process.env.NEYNAR_API_KEY; if (!neynarApiKey) { throw new Error('NEYNAR_API_KEY environment variable is not set'); } try { // Call Neynar API to search for the user const response = await fetch( `https://api.neynar.com/v2/farcaster/user/search?q=${encodeURIComponent(username)}`, { headers: { accept: 'application/json', 'x-api-key': neynarApiKey, }, }, ); if (!response.ok) { throw new Error( `Neynar API error: ${response.status} ${response.statusText}`, ); } const data = (await response.json()) as NeynarUserResponse; // Check if any users were found if (!data.result.users || data.result.users.length === 0) { return JSON.stringify({ success: false, message: `No Farcaster user found with username: ${username}`, }); } // Find the user with the matching username (case-insensitive) const user = data.result.users.find( (u) => u.username.toLowerCase() === username.toLowerCase(), ); if (!user) { return JSON.stringify({ success: false, message: `No Farcaster user found with username: ${username}`, }); } // Check if the user has any verified Ethereum addresses if ( !user.verified_addresses?.eth_addresses || user.verified_addresses.eth_addresses.length === 0 ) { return JSON.stringify({ success: false, message: `User ${username} has no verified Ethereum addresses`, }); } // Return the primary Ethereum address if available, otherwise the first one const ethAddress = user.verified_addresses.primary?.eth_address || user.verified_addresses.eth_addresses[0]; return JSON.stringify({ success: true, username: user.username, fid: user.fid, ethAddress, }); } catch (error) { return JSON.stringify({ success: false, message: `Error resolving Farcaster username: ${error instanceof Error ? error.message : String(error)}`, }); } } supportsNetwork(network: Network): boolean { return network.chainId === String(base.id); } }