Wallet Setup

To use paid Bismuth APIs, you need a small amount of USDC (a US dollar stablecoin) on the Base network. This guide walks you through the complete setup — from installing a wallet to exporting your private key for use with the MCP server.

You don’t need to be a crypto expert. Follow these steps and you’ll be ready to make your first paid API call.

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Wallet

Network

Fund

🔑 Key

1. Install MetaMask

   MetaMask is a browser extension wallet that runs in Chrome, Firefox, Brave, or Edge.

   
   MetaMask Install the browser extension wallet
   metamask.io →
   1. Click “Download” and install for your browser
   2. Open MetaMask and click “Create a new wallet”
   3. Create a password and write down your recovery phrase

   Protect your recovery phrase

   Never share your recovery phrase or private key with anyone. Anyone who has access to either can take your funds. Write your recovery phrase on paper and store it somewhere safe — not in a notes app or email.

2. Add the Base Network

   Base is a fast, low-cost Layer 2 network built on Ethereum. Most x402 API payments are fractions of a cent, and Base keeps those fees negligible.

   
   Base Add the network via chainlist.org (one click)
   chainlist.org →

   Search for “Base” and click “Add to MetaMask.” Or add it manually in MetaMask → Settings → Networks:

   Field	Value
   Network Name	Base
   RPC URL	https://mainnet.base.org
   Chain ID	8453
   Currency Symbol	ETH
   Block Explorer	https://basescan.org

   Note

   Base is a Layer 2 on Ethereum — transactions are fast and cheap. You’ll use ETH to pay gas fees (a few cents at most), and USDC to pay for API calls.

3. Get USDC on Base

   USDC is a stablecoin pegged 1:1 to the US dollar. $1 USDC = $1 USD, always. No price volatility — what you fund is what you spend.

   
   USDC Get stablecoins on the Base network
   Buy on Coinbase →

   Already have crypto? Bridge USDC from Ethereum to Base using bridge.base.org.

   Starting from scratch?

   1. Create an account on Coinbase
   2. Buy USDC (card or bank transfer)
   3. Withdraw to your MetaMask address on Base

   How much? Not much:

   • Screenshot or sentiment: $0.01 per call
   • Market overview: $0.05 per call
   • Intelligence report: $0.10 per call

   $1 covers 100 screenshot calls. $5 covers months of typical usage. Start small.

4. Export Your Private Key

   The x402 MCP server needs your private key to authorize payments automatically. It stays on your machine — it’s only used as an environment variable in your local config.

   To export from MetaMask:

   1. Open MetaMask and click your account icon (top right)
   2. Click “Account Details”
   3. Click “Show Private Key”
   4. Enter your MetaMask password to confirm
   5. Copy the private key — it starts with 0x and is 66 characters long

   Then add it to your config:

   ~/.cursor/mcp.json Your MCP client config

   
     "env": 
       "PRIVATE_KEY": "|"
     
   

   Keep your private key secure

   Your private key controls your wallet funds. Never paste it in chat, email, GitHub, or any website. Only use it as an environment variable in your local MCP config. If you ever suspect exposure, create a new wallet immediately and move your funds.

   Once you have the key, see Getting Started — Paid Mode for the exact config format for all 4 clients.

Security Tips

Use a dedicated wallet for x402 API payments — not your main crypto wallet. This limits exposure if your private key is ever compromised.

• Fund with small amounts. $1–$5 covers thousands of API calls.
• Never commit private keys to git. Use environment variables.
• Rotate keys if you suspect exposure. Create a new wallet, move funds, update your MCP config.
• The x402_network_info tool shows your wallet status — use it to confirm the server has picked up your key correctly.