register

Base Builder Code Registration

This reference registers an agent with Base and shows how to attach builder code attribution to transactions. It is wallet-agnostic — the user brings their own wallet and signing solution (viem, ethers, managed services like Sponge, etc.). This reference only handles registration and attribution.

Check if already registered

Before doing anything, check whether registration has already happened:

1. Look for a builderCode.ts file in the project (check src/constants/builderCode.ts or project root)

If it exists, registration is complete — do NOT re-register. Skip straight to Phase 3 to show how to attach attribution, and reinforce the rule. Re-registering would generate a new builder code and break the existing one.

If it's missing, proceed with the full registration flow below.

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Phase 1 — Wallet

Every agent needs a wallet to sign transactions. Ask the user before doing anything else.

1. Ask: "Do you have a wallet? If yes, share your wallet address."
2. If yes — take the wallet address they provide and move to Phase 2.
3. If no — direct them to the Base wallet setup guide: https://docs.base.org/ai-agents/guides/wallet-setup — do not proceed until they have a wallet and can provide their address.

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Phase 2 — Registration

Register the wallet with the Base builder code API. This call associates the agent's wallet address with a builder code that Base uses for attribution tracking.

Use the bundled scripts/register.sh (located at the skill root). It handles errors and extracts the builder code from the response:

BUILDER_CODE=$(bash scripts/register.sh "<wallet_address>")

Or call the API directly:

curl -X POST https://api.base.dev/v1/agents/builder-codes \
  -H "Content-Type: application/json" \
  -d '{"wallet_address": "<wallet_address>"}'

The API returns a response like:

{
  "builder_code": "bc_a1b2c3d4",
  "wallet_address": "0x...",
  "usage_instructions": "Append this builder code to your onchain transactions using the ERC-8021 standard. See: https://docs.base.org/base-chain/quickstart/builder-codes"
}