561 Group Market

Ordered JSON Pairs to UTF-8 Form Data

Serialize ordered JSON string pairs as application/x-www-form-urlencoded UTF-8. Preserve duplicate keys, blanks and order with native percent/space encoding. Up to 2048 pairs and 65536 canonical JSON/form bytes; refuse bad tuple types or Unicode before payment.

Price
from $0.0012 USDC per request (starting price; the 402 response quotes the exact amount for your input)
Network
Base mainnet, eip155:8453, settled in USDC through the Coinbase CDP facilitator
Method and URL
POST https://market.561.group/v1/data/json-to-form
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.

{
  "maxBytes": 102400,
  "bodySchema": {
    "type": "object",
    "additionalProperties": false,
    "required": [
      "pairs"
    ],
    "properties": {
      "pairs": {
        "type": "array",
        "maxItems": 2048,
        "items": {
          "type": "array",
          "minItems": 2,
          "maxItems": 2,
          "items": {
            "type": "string"
          }
        }
      }
    }
  }
}

Example request

{
  "method": "POST",
  "url": "https://market.561.group/v1/data/json-to-form",
  "headers": {
    "accept": "application/json",
    "content-type": "application/json"
  },
  "body": {
    "pairs": [
      [
        "x",
        "1"
      ],
      [
        "x",
        "2"
      ],
      [
        "note",
        "a + b"
      ]
    ]
  }
}

Output

{
  "schema": {
    "type": "object",
    "additionalProperties": false,
    "required": [
      "text"
    ],
    "properties": {
      "text": {
        "type": "string"
      }
    }
  },
  "example": {
    "text": "x=1&x=2&note=a+%2B+b"
  }
}

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 POST --header 'accept: application/json' --header 'content-type: application/json' --data-raw '{"pairs":[["x","1"],["x","2"],["note","a + b"]]}' --url 'https://market.561.group/v1/data/json-to-form'

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

Machine-readable