Body size · LIVE

BSA calculator x402 API for agents

Mosteller BSA

Agents must not invent BSA from model memory. This endpoint computes published Mosteller body surface area in m^2 from height and weight; pay per request with x402 USDC on Base.

LIVE $0.005 USDC GET /api/calc/bsa_mosteller

Markdown: /docs/bsa.md · Canonical: https://magentlab.com/docs/bsa

Not a medical device. Not a diagnosis, dose, or listing recommendation.

What it computes

Agents must not invent BSA from model memory. This endpoint computes published Mosteller body surface area in m^2 from height and weight; pay per request with x402 USDC on Base.

When to use

When an agent needs the cited Mosteller body-surface-area equation rather than a language-model guess, including for oncology dosing arithmetic. Pay per request with x402 USDC. Not a diagnosis or dosing recommendation.

When not to use

• Not a medical device. Not a treatment recommendation and not a dosing recommendation. The formula does not choose a regimen or round a vial.
• Height and weight must be provided in a consistent pair (cm/kg or in/lb).

Formula

BSA_m2 = sqrt((height_cm * weight_kg) / 3600)

Citation

Title

Simplified calculation of body-surface area

Authors

Mosteller RD

Source

N Engl J Med. 1987;317(17):1098

DOI

10.1056/NEJM198710223171717

Worked example

Also searched as

• Mosteller formula
• body surface area
• oncology BSA
• m2 BSA
• BSA calculator

Try

Opens the live endpoint. Unpaid browser requests show the paywall; agents should send Accept: application/json.

/api/calc/bsa_mosteller?height_cm=170&weight_kg=70

Full URL: https://api.magentlab.com/api/calc/bsa_mosteller?height_cm=170&weight_kg=70

Call

Expect HTTP 402 until you retry with PAYMENT-SIGNATURE. Incomplete query params return HTTP 400 before any quote or charge.

curl -i -H "Accept: application/json" "https://api.magentlab.com/api/calc/bsa_mosteller?height_cm=170&weight_kg=70"

Parameters

Bulk (POST)

POST the same path with a JSON items array. The first item is the GET unit; each additional item is $0.002. Invalid items return HTTP 400 before settlement.

POST /api/calc/bsa_mosteller Max 25 unit_amount + extra_item_amount * (n - 1) extra $0.002 PREVIEW

• 1 to 25 items. Each item uses the same keys as the GET query parameters.
• POST of 1 item costs the same as GET. Lists longer than 25: chunk into multiple POSTs. Extra items still execute; do not pad dummy rows.
• The first invalid item fails the whole request (index in the 400 JSON). You are not charged.
• HTTP 200 is {count, path, items}. Each items[i] is the GET 200 body for that row.
• Catalog misses (empty matches, found=false) stay paid 200s inside that slot.
• x402 resource URL is this path plus n and body_sha256. Browsers that prefer text/html get the same paywall as GET; Pay retries POST with the same items.

Example request (fixture)

{
  "items": [
    {
      "height_cm": "170",
      "weight_kg": "70"
    },
    {
      "height_cm": "170",
      "weight_kg": "70"
    }
  ]
}

Open bulk paywall →

Opens a two-item fixture on the API host. Unpaid browsers get the same MetaMask paywall as GET; Pay retries POST with those items.

Example 200 (fixture)

{
  "count": 2,
  "path": "/api/calc/bsa_mosteller",
  "items": [
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Mosteller RD",
        "doi": "10.1056/NEJM198710223171717",
        "id": "mosteller-1987",
        "source": "N Engl J Med. 1987;317(17):1098",
        "title": "Simplified calculation of body-surface area"
      },
      "formula": "mosteller",
      "formula_expression": "BSA_m2 = sqrt((height_cm * weight_kg) / 3600)",
      "weight_kg": 70.0,
      "height_cm": 170.0,
      "bsa_m2": 1.8181
    },
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Mosteller RD",
        "doi": "10.1056/NEJM198710223171717",
        "id": "mosteller-1987",
        "source": "N Engl J Med. 1987;317(17):1098",
        "title": "Simplified calculation of body-surface area"
      },
      "formula": "mosteller",
      "formula_expression": "BSA_m2 = sqrt((height_cm * weight_kg) / 3600)",
      "weight_kg": 70.0,
      "height_cm": 170.0,
      "bsa_m2": 1.8181
    }
  ]
}

Response

Example JSON

Machine form of the same example. Frozen fixture. Not a live lookup.

{
  "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
  "citation": {
    "authors": "Mosteller RD",
    "doi": "10.1056/NEJM198710223171717",
    "id": "mosteller-1987",
    "source": "N Engl J Med. 1987;317(17):1098",
    "title": "Simplified calculation of body-surface area"
  },
  "formula": "mosteller",
  "formula_expression": "BSA_m2 = sqrt((height_cm * weight_kg) / 3600)",
  "weight_kg": 70.0,
  "height_cm": 170.0,
  "bsa_m2": 1.8181
}

Client errors (HTTP 400)

Invalid params return 400 without charge. Shared HTTP 402 and 503 meanings: Payments.

Related tools

• BMI — Compute Keys/Quetelet body-mass index from height and weight, plus a WHO adult band.
• Devine IBW — Compute Devine ideal body weight and 0.4 adjusted body weight from height, sex, and actual weight.
• ANC — Compute absolute neutrophil count from WBC and neutrophil plus band percents, plus a Bodey 1966 granulocyte band.

Payment

Unpaid requests return HTTP 402 even if query parameters or POST items are missing or invalid, so CDP and agents can index the path. After a PAYMENT-SIGNATURE, invalid params return HTTP 400 JSON before settlement. magent does not charge. Fix the params, then request a new 402 quote for that complete URL. Catalog misses (empty matches, found=false) are valid paid 200s. Unpaid valid requests return HTTP 402 with a base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote: retry the same PAYMENT-SIGNATURE. Full handshake and shared payment errors: Payments. Stdio MCP: /docs/mcp.

Guarantees

• HTTP 402 is unpaid, including a missing query. After PAYMENT-SIGNATURE, invalid parameters return HTTP 400 before settlement. You are not charged. HTTP 402 never includes the tool JSON.
• exact: settlement finishes before the tool (paymentFlow upfront). batch-settlement: verify/deposit before the tool; chargedCumulativeAmount commits after HTTP 2xx. Uncertain or failed settlement fails closed (HTTP 503). Retry the same PAYMENT-SIGNATURE.
• HTTP 402 is unpaid only. Do not sign a second authorization because of a 503.
• Execution is timeout-bounded and concurrency-capped.
• Calculator inputs are stored encrypted for allowlisted operators (Magent Console). They are not in public logs, SSH lookups, catalog, or rollups. Request logs store path without query.