561 Group Market

RFC 9651 Structured Field Validation

Validate native RFC 9651 Item/List/Dictionary syntax. Return valid and canonical text or a paid syntax diagnostic. Up to 16384 ASCII field bytes and 65536 JSON bytes. Preserves typed decimals, dates, binary, Unicode Display Strings, ordered parameters and inner lists. Not a parser for legacy Accept, Cookie or Cache-Control fields. No model or upstream API.

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/http-field-validate
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": [
      "kind",
      "text"
    ],
    "properties": {
      "kind": {
        "type": "string",
        "enum": [
          "item",
          "list",
          "dictionary"
        ]
      },
      "text": {
        "type": "string",
        "maxLength": 16384,
        "description": "ASCII structured field value, up to 16384 bytes. Select its defined container; not legacy Accept, Cookie or Cache-Control grammar."
      }
    }
  }
}

Example request

{
  "method": "POST",
  "url": "https://market.561.group/v1/data/http-field-validate",
  "headers": {
    "accept": "application/json",
    "content-type": "application/json"
  },
  "body": {
    "kind": "dictionary",
    "text": "u=1, i"
  }
}

Output

{
  "schema": {
    "type": "object",
    "required": [
      "valid",
      "kind"
    ],
    "properties": {
      "valid": {
        "type": "boolean"
      },
      "kind": {
        "type": "string",
        "enum": [
          "item",
          "list",
          "dictionary"
        ]
      },
      "canonical": {
        "type": "string"
      },
      "message": {
        "type": "string"
      }
    }
  },
  "example": {
    "valid": true,
    "kind": "dictionary",
    "canonical": "u=1, i"
  }
}

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 '{"kind":"dictionary","text":"u=1, i"}' --url 'https://market.561.group/v1/data/http-field-validate'

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

Machine-readable