x402 Bazaar Listing Monitor MCP server

x402 Bazaar Listing Monitor

Scheduled watchdog for x402 sellers: polls Coinbase CDP's public Bazaar discovery catalog for the resources you register and alerts when one drops out or comes back — instead of finding out from a revenue dip days later.

Sellers who settle real x402 payments have no reliable way to confirm their resources stay discoverable in CDP's Bazaar catalog. The discovery API has a recurring, publicly-reported class of bug where a resource silently stops appearing despite confirmed settlements — sellers currently catch this only by manually re-running GET /discovery/merchant?payTo= on their own schedule.

This service automates that check: register your payTo address and the resource URLs you serve, and a scheduled poll diffs them against the live discovery catalog. State changes are recorded with timestamps, so you have a durable history you can cite if you need to escalate to CDP support.

MCP server

Endpoint: https://x402-listing-monitor.acjlabs.com/mcp (streamable HTTP)

One tool — no signup, no API key:

checklistinghealth

Checks whether a seller's x402 Bazaar resources are currently listed under a given payTo address in the public discovery catalog. Runs the same per-seller diff as the scheduled poller, on demand, for any payTo/resources pair — registered here or not.

Returns each resource flagged as listed or missing, as JSON.

HTTP API

Base URL: https://x402-listing-monitor.acjlabs.com

POST /register

{
  "sellerId": "your-slug",
  "payTo": "0x0000000000000000000000000000000000000000",
  "resources": ["https://api.example.com/your-resource"],
  "alertWebhookUrl": "https://example.com/hook"
}

loopback, .internal/.local hosts and URLs carrying credentials are rejected.

• sellerId — 2–64 characters: letters, digits, -, _
• payTo — 0x-prefixed, 40 hex characters
• resources — 1–200 http(s) URLs, no duplicates
• alertWebhookUrl — optional. A public https URL; alerts on your plan are POSTed to it. IP-literal,

• alertEmail — optional, and stored but not yet used: email delivery is not enabled (see Status).

Both contact fields are optional and registration succeeds without either. Supply neither and nothing is pushed to you — use GET /status below to check on your listings yourself.

Resources are watched by self-declaration: the service checks what you tell it to check. A sellerId that already exists is rejected rather than overwritten.

GET /status

GET /status?sellerId=your-slug&payTo=0x0000000000000000000000000000000000000000

Returns your own record: every resource you registered with its current status (listed, missing, payTo-mismatch, or null if no poll has reached it yet), its consecutive-miss count and last-checked timestamp, plus your most recent alerts and whether each was delivered.

Both sellerId and payTo are required and must match your registration; anything else returns 404. This is a knowledge check, not authentication — the data it returns is a diff against a public catalog. Your alertEmail and alertWebhookUrl are never echoed back, only reported as set or not set.

POST /poll

Runs the same poll the six-hourly cron runs, immediately, for every registered seller. Takes no body and returns counts only:

{ "polled": 2, "ok": 2, "failed": 0 }

Shortened. The full README is on GitHub.