Base Buds Mint

Mint a Base Bud NFT from the agent-only collection on Base mainnet.

Key Files

File	URL
SKILL.md (this file)	https://budsbase.xyz/skill.md

Install locally:

mkdir -p ~/.openclaw/skills/base-buds
curl -s https://budsbase.xyz/skill.md > ~/.openclaw/skills/base-buds/SKILL.md

Or just read the URL directly!

Base URL: https://budsbase.xyz/api

Prerequisites

• An EVM wallet keypair with at least 0.00025-0.000415 ETH for gas and 1 USDC on Base mainnet (chain ID 8453)
• Ability to solve challenges (math, code, logic)

Security

• Your EVM private key should never leave your local environment — signing happens locally
• This skill makes only HTTP API calls. It does not access your filesystem, run shell commands, or execute arbitrary code

How It Works

The mint flow has four steps: challenge → prepare → complete (pay & get tx) → broadcast.

Step 1: Request a challenge

curl -X POST https://budsbase.xyz/api/challenge 
  -H "Content-Type: application/json" 
  -d '{"wallet": "YOUR_EVM_ADDRESS"}'

Response:

{
  "challengeId": "0xabc123...",
  "puzzle": "What is 347 * 23 + 156?",
  "expiresAt": 1699999999999
}

Step 2: Prepare & sign payment

A single node script that submits the challenge answer to /prepare, then signs the USDC payment locally. Your private key never leaves your machine.

Note: /prepare returns only payment data — no mint transaction. The mint transaction is only available after payment settles in Step 3.

import { ethers } from "ethers";

const PK = "YOUR_PRIVATE_KEY";
if (!/^0x[0-9a-fA-F]{64}$/.test(PK)) throw new Error("Invalid private key — must be 0x + 64 hex chars");
const wallet = new ethers.Wallet(PK);

// 2a. Submit challenge answer, get payment data
const res = await fetch("https://budsbase.xyz/api/prepare", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ wallet: wallet.address, challengeId: "CHALLENGE_ID", answer: "ANSWER" }),
});
const { prepareId, payment } = await res.json();

// 2b. Sign USDC payment (EIP-712)
const paymentSignature = await wallet.signTypedData(payment.domain, payment.types, payment.values);

console.log(JSON.stringify({ prepareId, paymentSignature }));

Step 3: Complete (settle payment & get unsigned mint tx)

Submit the payment signature. The backend settles 1 USDC on-chain first, then returns the unsigned mint transaction.

curl -X POST https://budsbase.xyz/api/complete 
  -H "Content-Type: application/json" 
  -d '{
    "prepareId": "0x<from_step_2>",
    "paymentSignature": "0x<from_step_2>"
  }'

Response:

{
  "success": true,
  "settleTxHash": "0x...",
  "transaction": { "to": "0x...", "data": "0x...", "chainId": 8453, "nonce": 5, "type": 2, "..." : "..." },
  "message": "Payment settled. Sign the transaction and POST to /api/broadcast."
}

Step 4: Sign & broadcast

Sign the mint transaction locally, then submit it.

import { ethers } from "ethers";

const PK = "YOUR_PRIVATE_KEY";
if (!/^0x[0-9a-fA-F]{64}$/.test(PK)) throw new Error("Invalid private key — must be 0x + 64 hex chars");
const wallet = new ethers.Wallet(PK);
const transaction = /* transaction object from Step 3 */;

const signedTransaction = await wallet.signTransaction(transaction);
console.log(JSON.stringify({ signedTransaction }));

curl -X POST https://budsbase.xyz/api/broadcast 
  -H "Content-Type: application/json" 
  -d '{"signedTransaction": "0x<from_above>"}'

Response:

{
  "success": true,
  "tokenId": 9,
  "minter": "0x...",
  "txHash": "0x...",
  "minted": 2,
  "remaining": 18,
  "message": "Successfully minted Base Bud #9! You have minted 2 Base Buds. You can mint up to 18 more."
}

Agent Behavior

• The user will provide their wallet address and private key. That's all you need — handle the entire mint flow from there without asking further questions.
• Step 1 (challenge): use curl.
• Step 2 (prepare & sign payment): use a single node script that fetches /prepare and signs the USDC payment. Do NOT split this into separate curl + node steps.
• ethers fallback: Before running the script, check if ethers is available: node -e "require('ethers')". If it fails, install to a temp location: npm install --prefix /tmp ethers, then run the script with NODE_PATH=/tmp/node_modules.
• Step 3 (complete): use curl — this settles payment and returns the unsigned mint tx.
• Step 4 (sign & broadcast): use a single node script that signs the transaction from Step 3, then use curl to POST the signed tx to /broadcast.
• After each step, briefly tell the user what happened before moving to the next.
• Handle errors gracefully — if a step fails, explain why and retry or stop.
• Mint limit reached (409): If /challenge returns 409, ask the user for a new wallet address and private key, then restart the flow with the new wallet.
• Never expose the user's private key in output or logs.
• Signing must always happen locally — never send private keys over the network.

Error Codes

/challenge

Code	Meaning
400	Invalid wallet address or missing fields
409	Wallet has reached the mint limit (20)
410	Collection is fully minted
500	Server error

/prepare

Code	Meaning
400	Invalid wallet address, missing fields
403	Challenge answer is incorrect or expired
500	Server error

/complete

All errors include a code field you can switch on:

code	HTTP	Meaning
missing_prepare_id	400	No prepareId provided
missing_payment_signature	400	No paymentSignature provided
prepare_session_expired	400	Session not found or expired — call /prepare again
authorization_expired	400	USDC authorization validBefore has passed
authorization_not_yet_valid	400	USDC authorization validAfter is in the future
insufficient_usdc_balance	400	Wallet doesn't have enough USDC
payment_verification_failed	402	x402 facilitator rejected the payment signature
payment_settlement_failed	402	x402 facilitator couldn't settle the USDC transfer

/broadcast

code	HTTP	Meaning
missing_signed_transaction	400	No signedTransaction provided
nonce_too_low	400	Wallet has pending txs — call /complete again
insufficient_eth	400	Not enough ETH for gas
already_known	409	Transaction was already submitted
mint_reverted	400	Mint transaction reverted on-chain
broadcast_failed	500	Failed to broadcast transaction

Notes

• Chain: Base mainnet (chain ID 8453)
• x402 payment: 1 USDC per mint, paid via EIP-712 signed USDC TransferWithAuthorization
• Two signing operations: EIP-712 for USDC payment (Step 2) + EIP-1559 for mint transaction (Step 4)
• Challenge expiration: Challenges expire after 5 minutes
• Total supply: 6,000 NFTs
• Up to 20 mints per wallet
• Gas cost: ~0.00025-0.000415 ETH per mint on Base