Attribution Research
Builder Codes Research
How API20 tracks Builder Codes as future registry metadata for app-level attribution on x402 payments over Base.
What Builder Codes mean for API20
Builder Codes introduce an attribution layer for x402 payments on Base. They use ERC-8021 Schema 2 and can be added to settlement transaction calldata so x402 traffic can be attributed to a specific app or project.
API20 is tracking Builder Codes as future registry metadata — not as live settlement integration. See Coinbase Builder Codes docs for the upstream protocol context.
Why attribution matters for x402 APIs
As x402-powered APIs grow, developers need a way to document which apps, agents, or services may drive payment traffic. Registry metadata can help answer:
- Which builder or app should receive attribution for x402 settlement traffic?
- Which API entry maps to a known Builder Code?
- How might agent workflows reference attribution before a paid call?
How Builder Codes could fit into registry metadata
API20 may represent Builder Code fields alongside payment protocol, network, asset, and MCP-ready status:
Planned registry fields
builderCode— optional identifier (e.g. bc_example)attributionStandard— ERC-8021 Schema 2 researchappAttribution— planned app-level metadataserviceAttribution— planned service-level metadata
Preview with the planned command: api20 builder-code <api> — see commands.
Current status
Builder Code support is research/planned only. API20 does not attach Builder Codes to real x402 settlement transactions in the current version. No real payment execution is performed.
Disclaimer: API20 is an independent experimental project. It is not affiliated with Coinbase, Base, Coinbase Developer Platform, Tempo, Stripe, or any official x402, MCP, or MPP organization. Builder Codes references are for ecosystem research and educational purposes only.