# Obesity surgery mortality risk score (OS-MRS)

OS-MRS

Status: LIVE
Price: $0.005 USDC
`GET /api/calc/os_mrs`
HTML: https://magentlab.com/docs/os-mrs
Markdown: https://magentlab.com/docs/os-mrs.md

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

## What it computes

Sum the five DeMaria 2007 obesity surgery mortality risk score flags and return class A–C.

## When to use

When an agent needs the published OS-MRS point total and DeMaria 2007 class and must not invent a surgical-clearance decision or a mortality percentage.

## When not to use

- Not a medical device.
- Not a surgical clearance, cancellation, or monitoring order.
- Not a mortality percentage. Class A–C is the published DeMaria 2007 grouping, not a probability.
- magent does not weigh the patient and does not measure BMI or age. Each flag is caller-assigned.

## Formula

```
OS-MRS = bmi_ge_50 + male + hypertension + pe_risk_factors + age_ge_45; each 1 if true; max 5; class A 0-1, B 2-3, C 4-5
```

## Citation

[Obesity surgery mortality risk score: proposal for a clinically useful score to predict mortality risk in patients undergoing gastric bypass](https://doi.org/10.1016/j.soard.2007.01.005)
DeMaria EJ, Portenier D, Wolfe L
Surg Obes Relat Dis. 2007;3(2):134-140
DOI: [10.1016/j.soard.2007.01.005](https://doi.org/10.1016/j.soard.2007.01.005)

## Worked example

### All flags false

Given: `age_ge_45=false, bmi_ge_50=false, hypertension=false, male=false, pe_risk_factors=false`

1. score = 0
2. class A (0–1)


### All five flags true

Given: `age_ge_45=true, bmi_ge_50=true, hypertension=true, male=true, pe_risk_factors=true`

1. score = 5
2. class C (4–5)


## Also searched as

- OS-MRS
- obesity surgery mortality risk score
- DeMaria OS-MRS
- OSMRS
- bariatric mortality risk score
- gastric bypass mortality score
- DeMaria 2007

## Parameters

- `bmi_ge_50` (boolean, required): BMI ≥50 kg/m² (DeMaria 2007). true or false as assigned by the caller. magent does not weigh the patient or compute BMI.
- `male` (boolean, required): Male sex (DeMaria 2007). true or false as assigned by the caller. magent does not examine the patient.
- `hypertension` (boolean, required): Hypertension (DeMaria 2007). true or false as assigned by the caller. magent does not measure blood pressure.
- `pe_risk_factors` (boolean, required): Known PE risk: previous thromboembolism, preoperative vena cava filter, hypoventilation, or pulmonary hypertension (DeMaria 2007). true or false as assigned by the caller.
- `age_ge_45` (boolean, required): Age ≥45 years (DeMaria 2007). true or false as assigned by the caller. magent does not measure age.

## 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.

Method: `POST /api/calc/os_mrs`
Max items: 25
Price: unit_amount + extra_item_amount * (n - 1) (unit 5000 atomic, extra 2000 atomic)
Status: 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:

```json
{
  "items": [
    {
      "age_ge_45": "false",
      "bmi_ge_50": "false",
      "hypertension": "false",
      "male": "false",
      "pe_risk_factors": "false"
    },
    {
      "age_ge_45": "false",
      "bmi_ge_50": "false",
      "hypertension": "false",
      "male": "false",
      "pe_risk_factors": "false"
    }
  ]
}
```

Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/os-mrs

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/os_mrs",
  "items": [
    {
      "class": "A",
      "components": [
        {
          "factor": "bmi_ge_50",
          "points": 0,
          "present": false
        },
        {
          "factor": "male",
          "points": 0,
          "present": false
        },
        {
          "factor": "hypertension",
          "points": 0,
          "present": false
        },
        {
          "factor": "pe_risk_factors",
          "points": 0,
          "present": false
        },
        {
          "factor": "age_ge_45",
          "points": 0,
          "present": false
        }
      ],
      "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": "DeMaria EJ, Portenier D, Wolfe L",
        "doi": "10.1016/j.soard.2007.01.005",
        "id": "demaria-2007",
        "pmid": "17386394",
        "source": "Surg Obes Relat Dis. 2007;3(2):134-140",
        "title": "Obesity surgery mortality risk score: proposal for a clinically useful score to predict mortality risk in patients undergoing gastric bypass"
      },
      "formula": "os_mrs",
      "formula_expression": "OS-MRS = bmi_ge_50 + male + hypertension + pe_risk_factors + age_ge_45; each 1 if true; max 5; class A 0-1, B 2-3, C 4-5",
      "max_score": 5,
      "score": 0
    },
    {
      "class": "A",
      "components": [
        {
          "factor": "bmi_ge_50",
          "points": 0,
          "present": false
        },
        {
          "factor": "male",
          "points": 0,
          "present": false
        },
        {
          "factor": "hypertension",
          "points": 0,
          "present": false
        },
        {
          "factor": "pe_risk_factors",
          "points": 0,
          "present": false
        },
        {
          "factor": "age_ge_45",
          "points": 0,
          "present": false
        }
      ],
      "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": "DeMaria EJ, Portenier D, Wolfe L",
        "doi": "10.1016/j.soard.2007.01.005",
        "id": "demaria-2007",
        "pmid": "17386394",
        "source": "Surg Obes Relat Dis. 2007;3(2):134-140",
        "title": "Obesity surgery mortality risk score: proposal for a clinically useful score to predict mortality risk in patients undergoing gastric bypass"
      },
      "formula": "os_mrs",
      "formula_expression": "OS-MRS = bmi_ge_50 + male + hypertension + pe_risk_factors + age_ge_45; each 1 if true; max 5; class A 0-1, B 2-3, C 4-5",
      "max_score": 5,
      "score": 0
    }
  ]
}
```

## Response fields

- `formula` (string): os_mrs
- `formula_expression` (string): Exact expression used
- `score` (integer): OS-MRS points 0-5
- `max_score` (integer): 5
- `class` (string): DeMaria 2007 class A (0-1), B (2-3), or C (4-5). Not a surgical clearance or mortality probability.
- `components` (array): Per-flag points
- `citation` (object): DeMaria Surg Obes Relat Dis 2007 citation
- `disclaimer` (string): Not-a-device notice

## Example JSON

Frozen fixture. Not a live lookup.

```json
{
  "class": "A",
  "components": [
    {
      "factor": "bmi_ge_50",
      "points": 0,
      "present": false
    },
    {
      "factor": "male",
      "points": 0,
      "present": false
    },
    {
      "factor": "hypertension",
      "points": 0,
      "present": false
    },
    {
      "factor": "pe_risk_factors",
      "points": 0,
      "present": false
    },
    {
      "factor": "age_ge_45",
      "points": 0,
      "present": false
    }
  ],
  "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": "DeMaria EJ, Portenier D, Wolfe L",
    "doi": "10.1016/j.soard.2007.01.005",
    "id": "demaria-2007",
    "pmid": "17386394",
    "source": "Surg Obes Relat Dis. 2007;3(2):134-140",
    "title": "Obesity surgery mortality risk score: proposal for a clinically useful score to predict mortality risk in patients undergoing gastric bypass"
  },
  "formula": "os_mrs",
  "formula_expression": "OS-MRS = bmi_ge_50 + male + hypertension + pe_risk_factors + age_ge_45; each 1 if true; max 5; class A 0-1, B 2-3, C 4-5",
  "max_score": 5,
  "score": 0
}
```

## Errors

- HTTP 400 `invalid_flag`: boolean clinical flags must be true or false Returned before settlement; you are not charged.
- HTTP 400 `invalid_items`: POST body must be a JSON object with only an items array Returned before settlement; you are not charged.
- HTTP 400 `invalid_item_count`: items must be an array of 1 to 25 objects Returned before settlement; you are not charged.
- HTTP 400 `invalid_item`: each items entry must be a JSON object Returned before settlement; you are not charged.

Shared HTTP 402 and 503: https://magentlab.com/docs/payments

## Related tools

- [RCRI](https://magentlab.com/docs/rcri) — Sum the six Lee 1999 revised cardiac risk index factors and return class I–IV.
- [Gupta MICA](https://magentlab.com/docs/gupta-mica) — Compute the Gupta 2011 Table 2 logistic probability of 30-day myocardial infarction or cardiac arrest after surgery from age, ASA class, functional status, creatinine category, and surgery type.
- [Surgical Apgar](https://magentlab.com/docs/surgical-apgar) — Compute the Gawande 2007 intraoperative Surgical Apgar score from estimated blood loss, lowest mean arterial pressure, and lowest heart rate.

## 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.

- GET the tool with Accept: application/json (do not send Accept: text/html unless you want the human paywall).
- HTTP 402 means you have not paid. Decode the base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote.
- Sign accepts[0] (exact, EIP-3009) with validBefore = now + maxTimeoutSeconds (600 seconds), or accepts[1] (batch-settlement deposit/voucher) on product GET. Ping and POST {items} stay exact. Magent retries transient facilitator 429/5xx before answering.
- Retry the same URL with PAYMENT-SIGNATURE (base64 JSON of accepted and payload). Magent attaches canonical extensions.bazaar on CDP verify/settle; echoing 402 bazaar is optional.
- Success is HTTP 200 JSON plus PAYMENT-RESPONSE. exact settles before the tool. batch-settlement verifies (and deposit-settles) before the tool and commits the charge after HTTP 2xx. HTTP 503: retry the same PAYMENT-SIGNATURE. Mint a new exact nonce only after a new HTTP 402.

- offered `exact` on eip155:8453: Fixed-price USDC on Base. The buyer authorizes the advertised amount (EIP-3009). magent settles before the tool runs (paymentFlow upfront). extra.assetTransferMethod=eip3009 extra.paymentFlow=upfront.
- offered `batch-settlement` on eip155:8453: Payment-channel vouchers claimed later in batches. Exact stays accepts[0]. Same-path POST {items} is still exact. extra.assetTransferMethod=eip3009 extra.paymentFlow=authorization.

- not offered `upto`: Not offered. Usage-based: buyer authorizes a ceiling, seller settles the actual amount after work. Reserved for a future metered tool. Not for current calculators or code search.

Same-path POST {items} is still scheme exact: one EIP-3009 authorization for GET unit plus $0.002 per extra item. That is not x402 batch-settlement (payment channels / vouchers).

Shared HTTP 402 and 503 table: https://magentlab.com/docs/payments

Stdio MCP (one process per host): https://magentlab.com/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.