api.s2ar.dev

Live 402 challenge

Captured by the enrichment pass, not read just now. Prices can change — always read the 402 the endpoint answers with.

{
  "ok": false,
  "mcp": "https://api.s2ar.dev/mcp",
  "docs": "https://s2ar.dev/examples/score-a-sonnet.html",
  "free": {
    "note": "3 free score calls a day without an account on the plain route (not on /x402); sign in for a $0.50 grant (about 100 score calls)",
    "signup_url": "https://api.s2ar.dev/login",
    "per_day_keyless": 3,
    "signup_grant_usd": 0.5
  },
  "error": "payment required",
  "rails": [
    "x402",
    "credits"
  ],
  "accepts": [
    {
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "extra": {
        "name": "USD Coin",
        "version": "2"
      },
      "payTo": "0x2c4938626788e8e4fd803bfd1353eca64c1b5452",
      "scheme": "exact",
      "network": "base",
      "mimeType": "application/json",
      "resource": "https://api.s2ar.dev/x402/v1/score",
      "description": "Grade a text against a form — meter, rhyme, line and content gates, the dictionary named; a signed record. GET ?text=&form=",
      "maxAmountRequired": "5000",
      "maxTimeoutSeconds": 60
    }
  ],
  "charter": "https://api.s2ar.dev/charter",
  "evidence": "assay",
  "price_usd": 0.005,
  "witnesses": [
    "verifiers"
  ],
  "how_to_pay": "Pay per call with USDC on Base over x402 (no key: sign the 402's accepts[0], resend with PAYMENT-SIGNATURE); or buy a $5 pack by card and send Authorization: Bearer <key>; or add the MCP server at https://api.s2ar.dev/mcp. Money moves only after the answer exists; a failed call is never charged. Rules: https://api.s2ar.dev/charter.",
  "credits_mpp": {
    "url": "https://api.s2ar.dev/v1/credits/buy",
    "note": "cards via MPP need $0.50+, so buy a pack and use the key",
    "packs": [
      5,
      25,
      100
    ]
  },
  "determinism": "replayable",
  "example_get": "https://api.s2ar.dev/x402/v1/score?text=An+old+silent+pond%0AA+frog+jumps+into+the+pond%0ASplash%21+Silence+again&form=haiku",
  "proceedings": "https://api.s2ar.dev/.well-known/proceedings.json",
  "refund_rule": "a paid call that is not delivered is credited automatically and counted in the proceedings",
  "x402Version": 1,
  "checkout_url": "https://buy.stripe.com/dRm6oGeik0240Zr7q9dIA00",
  "credits_card": {
    "note": "a card checkout in a browser; the key is shown once after payment, then Authorization: Bearer <key>",
    "packs": {
      "5": "https://buy.stripe.com/dRm6oGeik0240Zr7q9dIA00",
      "25": "https://buy.stripe.com/bJe6oGfmo6qsdMd6m5dIA01",
      "100": "https://buy.stripe.com/4gM8wOeikcOQ4bD9yhdIA02"
    }
  },
  "expected_latency_ms": 300
}

Accepts

The payment requirements as published to the catalog. Read the live 402 before paying — a price here is a claim, not a quote.

[
  {
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "extra": {
      "name": "USD Coin",
      "version": "2"
    },
    "payTo": "0x2c4938626788e8e4fd803bfd1353eca64c1b5452",
    "scheme": "exact",
    "network": "eip155:8453",
    "mimeType": "application/json",
    "resource": "https://api.s2ar.dev/x402/v1/score",
    "description": "",
    "maxAmountRequired": "5000",
    "maxTimeoutSeconds": 60
  }
]

Provenance

Seen in the source catalog

2026-10-10 02:43Z

Last indexed by Roundhouse

2026-10-16 01:15Z

Last enriched (probe, favicon, geo)

2026-10-10 09:16Z

x402 version

1

Max timeout

60s

Liveness probe

HTTP 402