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AI agents operate autonomously and send transactions without a user manually triggering each one. Builder Codes give you a way to attribute all of that activity back to your agent’s identity on Base.

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Why agents need Builder Codes

  • Attribution — Every transaction your agent sends is tied to your identity in the Base registry. Without it, your agent’s onchain activity is anonymous.
  • Analytics — Track your agent’s transaction volume, user reach, and onchain conversion in base.dev.
  • Visibility — Agents with Builder Codes can appear in discovery surfaces like Base’s App Leaderboard and ecosystem spotlights.

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How it works

A Builder Code is a unique identifier (e.g. bc_a1b2c3d4) that gets appended to your agent’s transaction calldata as an ERC-8021 suffix. Smart contracts ignore the suffix; it is extracted by offchain indexers after the fact. The gas overhead is minimal (16 gas per non-zero byte).

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Register your agent

A single, unauthenticated API call: 
curl -X POST https://api.base.dev/v1/agents/builder-codes \
  -H "Content-Type: application/json" \
  -d '{"walletAddress": "<your-agent-wallet>"}'

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Next steps

Full registration guide

Step-by-step walkthrough including how to wire the ERC-8021 suffix into your transaction client