Merktop Wallet

Pay for any x402-gated API or resource (and get paid) from a non-custodial Merktop wallet on Base. Every payment is pulled just-in-time from the user's own wallet under a hard on-chain spend cap, so this skill can never spend beyond the budget the user set.

Merktop Wallet, pay (and get paid) for x402 resources

This skill lets you pay any x402-gated API, dataset, or service from a non-custodial Merktop wallet, and settle in USDC on Base. You never hold keys or funds: each payment is pulled just-in-time from the user's wallet through a spend permission they granted, and the on-chain spend cap is absolute, if a payment would exceed the budget, it fails instead of overspending.

When to use it

Use this when a task needs a resource that returns HTTP 402 Payment Required (paid APIs, agent-to-agent services, x402 data feeds, hosted paywalls). Do NOT use it for free endpoints.

Pay for a resource

Send the target x402 URL through the Merktop pay-proxy. It handles the whole 402 → pay → retry loop and streams the paid response back to you.

bash

# GET an x402 resource
curl -s "https://facilitator.merktop.com/buyer/$MERKTOP_BUYER_KEY/pay?url=https://seller.example/api/data"

# POST with a body (the body + content-type are forwarded to the seller verbatim)
curl -s -X POST "https://facilitator.merktop.com/buyer/$MERKTOP_BUYER_KEY/pay?url=https://seller.example/api/run" \
  -H "content-type: application/json" \
  -d '{"prompt":"..."}'

The proxy returns the seller's response body (use it as the result). The response header x-merktop-spent-cents tells you exactly what the call cost, so you can report spend back to the user.

Security: you can also send the key as the x-merktop-key header to https://facilitator.merktop.com/api/buyer/pay?url=<resource> instead of in the path, so it never appears in URL or proxy logs. Both forms work.

Read the outcome

• 2xx → paid and delivered; the body is the seller's response (the upstream status is passed through verbatim, so 201/204/206 are also success). Check x-merktop-spent-cents for the cost.
• 402 spend_cap_exceeded → the budget for this period is used up. Stop; tell the user to raise it.
• 402 no_permission → the user hasn't activated their agent / set a budget yet (see Setup).
• 401 invalid_buyer_key → MERKTOP_BUYER_KEY is missing or wrong.
• 403 recipient_blocked / sender_blocked → a sanctioned party; never retry.
• 429 rate_limited → back off and retry after the retry-after seconds.
• 502 pay_failed → the seller or settlement failed; the pull (if any) is swept back to the user's wallet on a best-effort basis (in the rare case the sweep-back also fails, Merktop records it for reconciliation). The spend claim is released, so retrying is generally safe, but verify the balance before assuming a refund landed.

Get paid (sell a resource)

To EARN, gate your own endpoint behind a Merktop hosted paywall and let other agents pay you in USDC, settled to your wallet by Merktop's facilitator:

1. Create a paywall in the Merktop app (https://facilitator.merktop.com/docs), pick your price and the URL it protects.
2. Share the public link https://facilitator.merktop.com/p/<your-slug>. Any agent (including ones running this skill) can pay it; the USDC lands in your wallet.

Rules of good behavior

• Only pay for resources the current task genuinely needs. Prefer free sources first.
• Treat x-merktop-spent-cents as real money, report it; don't loop on paid calls.
• Never try to bypass or exceed the cap. It is enforced on-chain; attempts just fail.
• Setup (one time, by the user): get a buyer key + set a budget at https://facilitator.merktop.com/docs, then put it in MERKTOP_BUYER_KEY.