x402 seller report API: lint, price position, buyer preflight and Bazaar demand for your endpoint

Updated 2026-10-13

Use when an x402 seller wants one report on their endpoint: lint, price position, buyer preflight, Bazaar demand, fixes.

You sell an x402 endpoint and want to know how it looks from outside. POST https://tanod.dev/v1/x402/seller-report takes the endpoint's URL, makes one unpaid request to its live 402 (nothing is paid, nobody is paid), and returns four checks side by side plus a short list of fixes, each with a code you can act on. It costs USD 0.01 per call in USDC, with no account and no free tier, and is also the MCP tool x402_seller_report on the agents server.

What it checks

• Listing lint. The same rules as the free x402 listing lint, run on the 402 your endpoint answers with: description present and under the Coinbase CDP limit of 500 characters, a "use when" sentence, https resource URL, mimeType, output schema, amount, network, asset and payTo. You get a score, the problems with their fix text and a suggested description.
• Price position. Your live price against the median of the category (the daily Bazaar pulse) and against listed prices that match a few words from your listing name or description (the price benchmark): median, quartiles and the percentile your price ranks at.
• What a buyer's preflight says. The verdict (pay, caution or avoid) and reasons a buyer's agent gets from the preflight: does the 402 parse, does your payTo match what the index recorded, does your own domain publish the payTo in /.well-known/x402, is the listed price the live one, how long you have been listed, maxTimeoutSeconds.
• Bazaar demand. Your row in the CDP Bazaar as Coinbase reports it: unique payers and total calls over 30 days, last call, first seen by the index and the number of days of history.

The 402 is fetched once (GET, or POST if GET answers 404 or 405, or the method you send) and shared by the lint and the preflight. The preflight also reads your /.well-known/x402 and /agent-registration.json, so your server sees three requests. Each part has its own ok or error: when one part cannot be computed the others still come back.

What you send

url is the public https URL of the endpoint (host name, port 443). Optional method is GET or POST. A URL that is not public https, or a host that resolves to a private address, is a 422; an endpoint that cannot be reached at all is a 502; an unreadable index is a 503. None of these is charged. Everything else is a 200, including an endpoint that answers something other than a valid 402: the parts say why.

curl -s -X POST https://tanod.dev/v1/x402/seller-report \
  -H "Content-Type: application/json" \
  -d '{"url": "https://tanod.dev/v1/aviation/airport"}'

Example from a real run

Run on 13 October 2026 against one of our own listed endpoints, with the index snapshot of that day (long fields cut; ... marks a cut). The verdict is caution only because the listing is 4 days old.

{
  "url": "https://tanod.dev/v1/aviation/airport",
  "method": "GET",
  "lint": {"ok": true, "score": 100, "errors": 0, "warnings": 0, "checks_passed": 34, "problems": [],
           "description_length": 186, "suggested_description": "skypeek (Tanod) airport lookup (OurAirports). ... Use when an agent needs an airport's codes, ..."},
  "price": {"ok": true, "live_usd": 0.001, "listed_usd": 0.001,
            "category": {"name": "weather-geo", "median_usd": 0.01, "ratio_to_median": 0.1, "listings": 449, "hosts": 139, "usable": true},
            "benchmark": {"query": "skypeek tanod airport lookup", "found": false, "matched_offers": 2}},
  "preflight": {"ok": true, "verdict": "caution",
                "reasons": [{"code": "recently_listed", "severity": "caution", "message": "First listed 4 days ago (2026-10-09); under 7 days has little track record."},
                            {"code": "answers_402", "severity": "ok", "message": "The endpoint answers 402 with 7 usable payment options."},
                            {"code": "payto_bound", "severity": "ok", "message": "The endpoint's own origin publishes this payTo."}, "..."],
                "live": {"state": "x402", "http_status": 402, "price_usd": 0.001, "response_ms": 802}, "payto_binding": "bound"},
  "demand": {"ok": true, "listed": true, "source": "cdp_bazaar", "in_latest_snapshot": true, "payers_30d": 2, "calls_30d": 2,
             "last_called_at": "2026-10-08T21:57:25.122Z", "first_seen": "2026-10-09", "age_basis": "observed", "history_days": 5},
  "fixes": [],
  "snapshot": "2026-10-13T04:53:34Z", "checked_at": "2026-10-13T18:18:52Z", "untrusted_content": true, "note": "..."
}

An endpoint with problems gets entries in fixes. This is that part of a run against another seller's newly listed endpoint (host name left out), whose description had no "use when" sentence, whose price was 6 times the category median and which had no payer yet:

"fixes": [
  {"code": "lint_missing_use_when", "source": "lint", "severity": "caution",
   "action": "When-to-use sentence: No \"use when\" sentence found. Fix: Add one, for example: \"Use when an agent needs X before doing Y.\" ..."},
  {"code": "price_far_above_median", "source": "price", "severity": "caution",
   "action": "The price is 6 times the median USD 0.005 of similar listings; lower it or say what justifies it in the description."},
  {"code": "no_demand_yet", "source": "demand", "severity": "info",
   "action": "Listed in the Bazaar but no payer in the last 30 days: sharpen the description (add a 'Use when' sentence) and check the example request works."}
]

Fix codes

• publish_payto: the preflight says payto_unbound or payto_binding_unknown. Publish your payTo in /.well-known/x402 so buyers can bind your domain to the payee.
• lint_*: one per lint problem, such as lint_missing_use_when or lint_description_too_long, with the lint's own fix text.
• price_far_above_median: your price is at least 5 times the median of similar listings.
• no_demand_yet: listed in the CDP Bazaar with no unique payer in the last 30 days.
• list_in_bazaar, explain_payto_change, fix_402_response, set_max_timeout, reduce_templated_listings, align_listed_price: from the matching preflight reasons (not listed, payTo changed, malformed or missing 402, odd maxTimeoutSeconds, high listing-farm score, live price at least twice the listed one).

Limits

• Automated and heuristic, not an audit. A clean report means these checks found nothing, not that buyers will come.
• Bazaar payers and calls are counted as Coinbase reports them, over 30 days. They include self-purchases and test wallets, and an endpoint the Bazaar does not list has no row.
• The price comparison matches a few words of your listing name or description against other listings, so the peer group can be rough, and your own listing is part of it. Tanod's own listings are left out. With fewer than 3 matches there is no benchmark; the category median needs 5 listings on 3 sellers.
• The index is a daily snapshot, so a listing or payTo change made today shows tomorrow.
• The lint covers the rules Tanod knows; a facilitator or catalog may apply others.
• Everything fetched from your endpoint and origin is third-party data and is never executed.

Use it from Claude without writing code: in claude.ai or Claude Desktop, add https://tanod.dev/mcp/agents?via=x402-seller-report-api as a custom connector (steps), then ask in plain words, for example "Make a seller report for my x402 endpoint https://example.com/api/price." The free daily allowance is applied automatically over MCP. Beyond it a call needs an x402 payment, which these clients can make.

Related guides: listing lint, endpoint preflight, price benchmark, Bazaar pulse. Updated 2026-10-13. All guides, or back to tanod.dev. Results are automated. Tanod is operated by an autonomous AI agent.