561 Group Market

x402 Market Observation

Sampled Base USDC EIP-3009 AuthorizationUsed activity with provider provenance and explicit arithmetic extrapolation; it does not identify x402 use or agent identity.

Price
$0.10 USDC per request
Network
Base mainnet, eip155:8453, settled in USDC through the Coinbase CDP facilitator
Method and URL
GET https://market.561.group/v1/x402-market/observation
Response type
application/json
Seller
Causeway Services (561 Group)

Input contract

Input that fails this contract is refused with a 4xx status before any payment is requested.

{
  "querySchema": {
    "type": "object",
    "properties": {
      "windowBlocks": {
        "type": "integer",
        "minimum": 30,
        "maximum": 10800,
        "default": 900,
        "description": "Block-count sample window ending near a public-provider chain tip; the response distinguishes measured range from arithmetic extrapolation."
      }
    }
  }
}

Example request

{
  "method": "GET",
  "url": "https://market.561.group/v1/x402-market/observation?windowBlocks=900",
  "headers": {
    "accept": "application/json"
  }
}

Output

{
  "schema": {
    "type": "object",
    "required": [
      "recordType",
      "observedAt",
      "chain",
      "measured",
      "extrapolated",
      "caveat"
    ],
    "properties": {
      "recordType": {
        "type": "string"
      },
      "observedAt": {
        "type": "string"
      },
      "chain": {
        "type": "object"
      },
      "measured": {
        "type": "object"
      },
      "distinctAuthorizersSampled": {
        "type": "integer"
      },
      "extrapolated": {
        "type": "object"
      },
      "caveat": {
        "type": "string"
      }
    }
  },
  "example": {
    "recordType": "561-group.x402-market-observation",
    "observedAt": "2026-08-28T02:00:00.000Z",
    "chain": {
      "network": "eip155:8453",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "rangeObservation": true
    },
    "measured": {
      "fromBlock": 50546711,
      "toBlock": 50547611,
      "blocks": 900,
      "approximateMinutes": 30,
      "authorizations": 812,
      "distinctAuthorizers": 96
    },
    "distinctAuthorizersSampled": 96,
    "extrapolated": {
      "dayFactor": 48,
      "monthFactor": 1440,
      "authorizationsPerDay": 38976,
      "authorizationsPer30Days": 1169280,
      "basis": "a 900-block sample scaled by 48.0 to a day; a burst inside the window is scaled with it"
    },
    "caveat": "EIP-3009 AuthorizationUsed is not an x402 marker or an agent identity. Daily and monthly figures are arithmetic projections from this sampled range, not established bounds."
  }
}

How to buy with x402

  1. Send the request without payment. The server answers 402 Payment Required with a base64 JSON PAYMENT-REQUIRED header holding the amount, asset, network and payee.
  2. Have your wallet sign an EIP-3009 transferWithAuthorization for exactly those terms (an x402 client library does this for you).
  3. Repeat the identical request with the signed payload in the PAYMENT-SIGNATURE header.
  4. The server verifies, runs the operation, settles, and returns 200 with the result and a PAYMENT-RESPONSE header carrying the settlement receipt.

Read the price without paying

curl --include --request GET --header 'accept: application/json' --url 'https://market.561.group/v1/x402-market/observation?windowBlocks=900'

This request authorizes nothing; it returns the live payment terms. Read the full explanation of x402.

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