tollgate

I started this because KeeperHub's homepage promises you can "publish a workflow, earn per call" but when I looked at their actual API, that producer-side wasn't there. PUT /go-live only accepted {name, publicTagIds}. The open-source repo had zero hits for x402. So I built the missing piece.

tollgate is two things: a CLI that turns any KeeperHub workflow into an x402-paid HTTP endpoint, and matched TypeScript + Python SDKs that let agents discover, pay for, and call those endpoints. The flow: author runs keeperhub-publish wf_xyz --price 0.02, the gateway hosts an x402-gated route, agents pay USDC via Coinbase's facilitator, the gateway calls KeeperHub's execute API on the author's behalf, results flow back.

I built two real reference workflows on KeeperHub to demo this end-to-end. TokenSafetyCheck reads a token's name, symbol, decimals, and totalSupply from any Base-mainnet ERC-20 for $0.02. StablecoinPriceCheck reads USDC's totalSupply and paused() state for $0.03 - a real depeg precursor signal. The reference agent calls both, composes a "should I swap?" recommendation, and prints the real $0.05 spent on Base Sepolia. Every transaction is verifiable on Basescan.

Mid-build, KeeperHub shipped their own ERC-8004 listing toggle which partially solved the problem I started with. So I refactored the pitch: tollgate now sits adjacent to their marketplace as the HTTP-only discovery layer (no on-chain registry reads required) and the paywall for any non-listed workflow. Both my reference workflows ship listed on KH's marketplace AND callable via tollgate.

The gateway is a Hono server on Node 20 one Dockerfile, deploys to Coolify / fly.io / any container host with a persistent volume. The TypeScript SDK wraps x402-fetch + viem for agent-side EIP-3009 signing and budget caps. The Python SDK is at full API parity using httpx + eth_account + the official x402>=2.9 package, with respx-mocked unit tests plus a real-gateway integration test in CI. 56 tests total across both languages.

The hardest part wasn't the x402 protocol. Coinbase ships a hosted facilitator that handles verify + settle on-chain for you. It was figuring out KeeperHub's API contract, because most of it isn't documented. I tested four different request body shapes against POST /workflow/{id}/execute to find the one that actually carried tokenAddress through to the workflow (it's {input: {...}}). I discovered the workflow's output lives at /logs under execution.output, not at /status like you'd expect.

Mid-build, KeeperHub shipped their ERC-8004 listing UI. I had to update my positioning instead of competing with their listing, tollgate now sits adjacent. I built both reference workflows on KH's canvas using their Read Contract + Run Code action nodes. KH's Run Code wraps return values as {logs, result, success} with no UI to unwrap, so the gateway auto-unwraps that envelope at the SDK boundary.

One thing I'm proud of: the gateway is fail-closed. If KeeperHub's execute call fails after the agent has signed the EIP-3009 authorization, the gateway never calls the facilitator's settle endpoint so the caller is never charged for nothing. Verified on-chain: in early testing, when my workflow IDs weren't real yet, every paid attempt returned 502 from the gateway and the agent's USDC balance stayed exactly the same.