erc8021-attribution

ERC-8021 Builder Code Attribution

When this skill applies

Trigger when:

• The user is building on Base and wants to track which agents/developers drive transactions
• The user wants to share protocol fees with the referrer of a transaction
• The user is integrating with protocols that support Builder Code (Aerodrome, Morpho, GBLIN, etc.)

What ERC-8021 is

ERC-8021 is the Builder Code standard on Base — a way to attribute on-chain transactions to the developer or agent that referred them. Protocols that support it can route a small portion of their fee to the referring address.

Format: bc_<8 alphanumeric characters>. Example: bc_gbdo32j0.

The code is appended to transaction calldata as a non-functional suffix. Protocol contracts can read it and apply revenue-share logic.

How to register a Builder Code

1. Go to https://base.dev/builders
2. Sign in with a Base Smart Wallet
3. Generate a Builder Code linked to your wallet address
4. Save the code

The Builder Code is portable — you can use it across any protocol that supports ERC-8021.

Integration pattern: append Builder Code to calldata

import { encodePacked } from 'viem';

const BUILDER_CODE = process.env.BUILDER_CODE; // e.g. 'bc_gbdo32j0'

function appendBuilderCode(originalCalldata: `0x${string}`): `0x${string}` {
  if (!BUILDER_CODE) return originalCalldata;
  const codeBytes = Buffer.from(BUILDER_CODE, 'utf-8').toString('hex');
  return `${originalCalldata}${codeBytes}` as `0x${string}`;
}

Protocols that support ERC-8021 on Base (as of May 2026)

Protocol	Status	Fee share to builder
GBLIN	Live	0.025% of transaction value (half of founder fee)
Aerodrome	Live	Varies by pool
Morpho Base	Partial	Via separate referral program

Check the live registry: https://base.dev/builders/registry

Pattern: pass referrer through your MCP tool

If your MCP server helps agents transact on Base, expose the Builder Code in the response so the receiving agent knows the referral chain: