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Getting Started with AgentKit on Flow

AgentKit is an ecosystem-agnostic modular developer toolkit that lets you rapidly build, deploy, and iterate on AI agents using pre-configured environments and ready-to-use templates.

In this guide, you'll set up your own custom agent running on Flow's EVM-compatible testnet, powered by Langchain and Anthropic's Claude LLM.

Quickstart - Starting From Scratch​

Open your terminal and run:


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npm create onchain-agent@latest

Follow the interactive setup:

  1. Type y to proceed, then press Enter.
  2. Select your framework: Langchain
  3. Choose your network: EVM
  4. Set the custom Chain ID:
    • 545 for Flow Testnet
    • 747 for Flow Mainnet
  5. JSON-RPC endpoint:

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    https://testnet.evm.nodes.onflow.org

Project Setup​

Once your scaffold is ready:


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cd onchain-agent
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npm install

Now open the project in your preferred IDE (e.g. Cursor).

Environment Configuration​

  1. Create a .env.local file (or edit the one generated).
  2. Add your API keys (we'll use Anthropic here).

You can also use OpenAI, DeepSeek, or any other supported LLM.

Get Your Anthropic API Key​

  • Head to Anthropic Console
  • Create an account and purchase credits
  • Click Create Key, name it, and copy the API key
  • Add this to your .env.local:

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ANTHROPIC_API_KEY=your_api_key_here

Wallet Setup with MetaMask​

  1. Add Flow Testnet to MetaMask
  2. Use the Faucet to fund your wallet
  3. Get your private key:
    • Click the ... menu in MetaMask > Account Details
    • Enter your password, copy the private key
  4. Add it to .env.local:

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PRIVATE_KEY=your_private_key_here

Your .env.local should look something like this:


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PRIVATE_KEY=...
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ANTHROPIC_API_KEY=...

Now run:


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mv .env.local .env
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npm run dev

Visit your local server:


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http://localhost:3000

Configure Your LLM​

If your agent doesn't respond yet — no worries! You still need to configure your LLM and client libraries.

Choose a Model​

Langchain supports many LLMs (full list here).

For this example, we'll use Anthropic's claude-3-5-haiku-20241022, a lightweight and affordable model. Alternatively, DeepSeek is highly recommended for budget-friendly usage.

Update create-agent.ts​

Change the default model from OpenAI:


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const llm = new ChatOpenAI({ model: 'gpt-4o-mini' });

To Anthropic:


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import { ChatAnthropic } from '@langchain/anthropic';
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const llm = new ChatAnthropic({ model: 'claude-3-5-haiku-20241022' });

Install the package:


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npm install @langchain/anthropic

Configure Flow and Viem Wallet​

Update the Faucet Provider Logic​

Change this:


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const canUseFaucet = walletProvider.getNetwork().networkId == 'base-sepolia';

To:


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const canUseFaucet = walletProvider.getNetwork().networkId == 'flow-testnet';

Add Flow Context Message to Agent​

This gives your agent context about the Flow testnet:


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const flowContextMessage = canUseFaucet
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? `
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You are now operating on the Flow blockchain testnet using a Viem wallet. Flow is a fast, decentralized, and
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developer-friendly blockchain designed for NFTs, games, and apps.
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Key facts about Flow:
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- Flow uses a proof-of-stake consensus mechanism
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- The native token is FLOW
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- Flow has a unique multi-role architecture for high throughput
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- The testnet is EVM-compatible (works with MetaMask + Viem)
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- RPC URL: https://testnet.evm.nodes.onflow.org
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- Chain ID: 545
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Your wallet address is \${await walletProvider.getAddress()}.
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`
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: '';

Then inject it into the agent message modifier:


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agent = createReactAgent({
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llm,
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tools,
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checkpointSaver: memory,
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messageModifier: `
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You are a helpful agent interacting with the Flow blockchain testnet using a Viem wallet.
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Flow testnet supports EVM, so you can use Ethereum-compatible tools.
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\${flowContextMessage}
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Before your first action, check the wallet details. If you see a 5XX error, ask the user to try again later.
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If a task is unsupported, let the user know and point them to CDP SDK + AgentKit at:
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https://docs.cdp.coinbase.com or https://developers.flow.com.
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Be concise, helpful, and avoid repeating tool descriptions unless asked.
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`,
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});

You're Done!​

You now have a working AI agent connected to Flow testnet using AgentKit!

You can send faucet tokens to your wallet and start testing smart contract interactions or on-chain workflows.

Starter Project​

Want to skip the setup?

Fork the Flow AgentKit Starter

This starter includes all necessary config to start building immediately on Flow.

Adding AgentKit to an Existing Project​

Already have a project and want to add AgentKit? Follow these steps to integrate it into your existing codebase:

Install the Package​

Run this command in your project's root directory:


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npm install onchain-agent@latest

This will:

  • Download and install the latest version of the onchain-agent package
  • Add it to the dependencies section of your package.json
  • Update your node_modules folder accordingly

Configure Environment​

  1. Create or update your .env file with the necessary API keys:

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PRIVATE_KEY=your_wallet_private_key
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ANTHROPIC_API_KEY=your_anthropic_api_key
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# Or other LLM API keys

  1. Configure your RPC endpoints for Flow:

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FLOW_TESTNET_RPC_URL=https://testnet.evm.nodes.onflow.org
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FLOW_MAINNET_RPC_URL=https://mainnet.evm.nodes.onflow.org

Integrate AgentKit in Your Code​

Import and configure AgentKit in your application:


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// Import AgentKit components
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import { createReactAgent, ChatAnthropic } from 'onchain-agent';
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import { createWalletClient, http, createPublicClient } from 'viem';
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// Set up your Flow wallet provider
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const walletClient = createWalletClient({
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transport: http('https://testnet.evm.nodes.onflow.org'),
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chain: {
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id: 545, // Flow Testnet
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name: 'Flow Testnet',
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},
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account: yourPrivateKey,
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});
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// Configure the LLM
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const llm = new ChatAnthropic({
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model: 'claude-3-5-haiku-20241022',
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});
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// Create your agent
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const agent = createReactAgent({
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llm,
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tools: yourSelectedTools,
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// Additional configuration
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});
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// Use the agent in your application
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// ...

Add Specialized Tools (Optional)​

To add specialized blockchain tools to your agent:


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import { viem, ViemToolConfig } from 'onchain-agent';
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// Configure Viem tools for Flow
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const viemTools = viem.createTools({
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chain: {
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id: 545,
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name: 'Flow Testnet',
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},
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transport: http('https://testnet.evm.nodes.onflow.org'),
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} as ViemToolConfig);
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// Add these tools to your agent
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const agent = createReactAgent({
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llm,
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tools: [
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...viemTools,
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// Other tools
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],
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});

Resources​

Happy hacking on Flow!

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