Inspiration I was inspired to build an onchain AI agent marketplace after realizing how difficult it still is for people to reliably use, test, and pay for AI agents, especially when payments, wallets, and infrastructure are involved.
What it does:
The platform, Agent Bazaar, aims to let users browse agents, run them instantly, and pay with seamless onchain flows using x402 and Exact EVM Payments.
How we built it
I used Next.js, TypeScript, Base Mainnet, Viem, and x402 AgentKit to dynamically load agents, assemble payment payloads, and implement typed-data signing for ERC-3009 authorizations.
Challenges we ran into
The hardest part was repeatedly hitting 402 payment errors and EIP-712 domain mismatches, which forced me to deeply examine signer addresses, verifying contracts, domain structure, and how Exact EVM verifies signatures; these issues are still not fully resolved.
Accomplishments that we're proud of
I’m proud of building a functional marketplace UI, integrating the x402 flow end to end, and learning the underlying cryptographic and protocol-level mechanics instead of relying on abstractions
What we learned
I gained deep understanding of ERC-3009, EIP-712 domain hashing, wallet-client behavior in Viem, Base’s signing expectations, and how sensitive typed-data verification is to small inconsistencies.
What's next for Untitled
I hope to finish debugging the domain-matching issues, get guidance from someone on the Base team, expand the agent catalog, and eventually ship a polished onchain agent marketplace that anyone can use.
Built With
- next.js
- typescript
- x402
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