Coal
Agent-payable checkout
Six months ago I tried to charge an AI agent for an API call. It needed to pay about $0.001 to run a single query.
At the time, the options were:
Give the agent a credit card (it’s an agent, there’s no card holder)
Make a human sign up and attach Stripe (kills the agent-only flow)
Let it scrape for free (what’s happening to a lot of small APIs right now)
That’s how Coal started.
Coal is one checkout where both humans and AI agents can pay. Humans tap “Pay with USDC”. Agents pay per-call via x402 or OKX App. Both settle directly into the merchant’s wallet on Base. Three lines of code on the merchant side.
What it looks like:
For a human paying: a checkout that accepts USDC, ETH, or any token swappable on Base (routed via LiFi). Settles in USDC to the merchant.
For an AI agent paying: drop the
coal-reactnpm package in front of your existing API. The agent hits your endpoint, gets HTTP 402 with the price, pays in USDC, retries with proof, and receives the response. Existing subscriber flows do not change.
Where it is right now (May 2026):
Live at https://usecoal.xyz
npm package
coal-reactv0.4.1Real payments settling on Base mainnet. Every payment is publicly verifiable at usecoal.xyz/verify/[id] with a three-step proof trail (signed, confirmed on Base, published as a tamper-proof receipt)
First merchants testing the human checkout flow
The wedge is small API publishers: solo devs running scrapers or data APIs. Their endpoints are getting hit by GPT bots and agents, and they are capturing none of it. Coal opens that up as a second revenue stream without changing existing subscriber traffic.
Right now I am onboarding 10 design partners at 0% Coal fee indefinitely. I handle integration with them.
What I am looking for:
If you publish an API anywhere and you are seeing agent traffic, would you try Coal as a second rail? No fee for design partners, I handle integration.
If you have thought about agent-payable APIs but could not implement it, what is the single biggest blocker?
If you have agent traffic hitting endpoints you would want to charge for, what is stopping you today?
Honest feedback, especially critical takes, is useful.
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