Builder Codes for Agents

Register your agent on Base.dev and append a Builder Code to every transaction to measure onchain activity.

Base.dev is the canonical registry for agents on Base. A Builder Code ties every transaction your agent sends to your identity in that registry, giving you verifiable onchain attribution and access to analytics and leaderboard features.

What you get

• Builder Code — a unique identifier (e.g. bc_a1b2c3d4) that you append to your onchain transactions. Base uses this to measure your agent’s activity on Base Chain.

Prerequisites

• An EVM wallet address that your agent operates from

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Get your Builder Code

A single, unauthenticated API call:

Terminal

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

Response:

Response

{
  "builderCode": "bc_a1b2c3d4",
  "walletAddress": "0x...",
}

Already registered? Calling this endpoint again with the same wallet address returns your existing builder code.

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Get a Builder Code using the Base skill

If you’re using an AI coding tool (Claude Code, Cursor, Codex), install the Base skills package and let the skill handle registration end-to-end:

Terminal

npx skills add base/skills

Then ask your agent: “Register my agent for a builder code on Base.dev.”

The skill runs three phases:

1. Wallet

   Asks for your agent’s wallet address. If you don’t have one, it sends you to the wallet setup guide before continuing.

2. Registration and attribution

   Calls POST /v1/agents/builder-codes with your wallet address, writes the returned code to src/constants/builderCode.ts, installs ox, and wires the ERC-8021 dataSuffix into your transaction client (viem, ethers.js, or managed service). It also writes an AGENT_README.md documenting the setup.

3. Permanent rule

   Confirms the setup and instructs you that every future transaction must include the ERC-8021 suffix. Missing it causes silent, permanent attribution loss.

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Get a Builder Code with a prompt

If you’re using an AI agent, point it to this page:

Prompt

Get a Builder Code for my agent on Base.dev using the documentation at https://docs.base.org/ai-agents/setup/agent-builder-codes.

My agent's wallet address: [0x...]

Run this curl command, replacing the wallet address with my agent's:
curl -X POST https://api.base.dev/v1/agents/builder-codes \
  -H "Content-Type: application/json" \
  -d '{"walletAddress": "0x..."}'

Return the `builderCode` from the response, then show me how to append it to my transactions using ERC-8021.

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What happens next

Once you receive your Builder Code, it becomes active right away and Base will begin tracking any transactions that include it.

API Reference

Get builder code

POST /v1/agents/builder-codes

No authentication required.

Field	Type	Required	Description
walletAddress	string	Yes	Your agent’s EVM wallet address (0x...)

Returns the builder code for the given wallet. The same wallet address always returns the same code and is safe to call multiple times.

Further reading

• Builder Codes Overview - What Builder Codes are, how ERC-8021 attribution works, and FAQs on gas, identity, and wallet support
• Builder Codes for Agent Developers - API reference, skill reference, and overview