Get a Builder Code for Your Agent

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

One call. No auth.

Terminal

curl -X POST https://api.base.dev/v1/agents/builder-codes \
  -H "Content-Type: application/json" \
  -d '{
    "wallet_address": "0x<your-wallet-address>"
  }'

Response:

Title Response

{
  "builder_code": "bc_a1b2c3d4",
  "wallet_address": "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 four 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 — no error, no warning.

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Get a Builder Code with a prompt

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

Title Prompt

Get a Builder Code for my agent on Base.dev using the documentation at [URL of this page].

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

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

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

---

What happens next

Your Builder Code starts working immediately — Base will measure any transaction that includes it.

API reference

Get builder code

POST /v1/agents/builder-codes

No authentication required.

Field	Type	Required	Description
wallet_address	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 — safe to call multiple times.