561 Group Market

Heart-Rate Threshold

Heart-Rate Threshold: the Workwell Foundation resting-heart-rate+15bpm pacing-ceiling heuristic, labeled as an unvalidated clinical rule of thumb. Stateless: nothing submitted or computed is stored.

Price
$0.01 USDC per request
Network
Base mainnet, eip155:8453, settled in USDC through the Coinbase CDP facilitator
Method and URL
POST https://market.561.group/v1/pacing/heart-rate-threshold
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",
    "properties": {
      "restingHr": {
        "type": "number",
        "exclusiveMinimum": 0,
        "description": "Resting heart rate in beats per minute."
      }
    },
    "required": [
      "restingHr"
    ]
  }
}

Example request

{
  "method": "POST",
  "url": "https://market.561.group/v1/pacing/heart-rate-threshold",
  "headers": {
    "accept": "application/json",
    "content-type": "application/json"
  },
  "body": {
    "restingHr": 58
  }
}

Output

{
  "schema": {
    "type": "object",
    "required": [
      "ceilingBpm",
      "restingHr",
      "formula",
      "evidenceStatus"
    ],
    "properties": {
      "ceilingBpm": {
        "type": "number"
      },
      "restingHr": {
        "type": "number"
      },
      "formula": {
        "type": "string"
      },
      "evidenceStatus": {
        "type": "string"
      }
    }
  },
  "example": {
    "ceilingBpm": 73,
    "restingHr": 58,
    "formula": "resting heart rate + 15 bpm",
    "evidenceStatus": "Workwell Foundation clinical rule of thumb; no validating primary study found (targeted PubMed search, 2026-09-01). Present as an informal heuristic, never as a validated instrument."
  }
}

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 '{"restingHr":58}' --url 'https://market.561.group/v1/pacing/heart-rate-threshold'

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

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