# HEAVEN criteria

HEAVEN

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

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

## What it computes

Apply the Davis 2017 HEAVEN criteria from six caller-assigned flags and return high_risk iff any is true, plus the count of criteria met (0-6).

## When to use

When an agent already has the six Davis 2017 HEAVEN flags (hypoxemia, extremes of size, anatomic challenges, vomit/blood/fluid, exsanguination, limited neck mobility) and needs whether any published difficult-airway criterion is present. magent does not measure SpO2 or examine the airway.

## When not to use

- Not a medical device.
- Not an intubation order.
- magent does not measure SpO2 or examine the airway. The caller assigns the six flags.
- Not Mallampati, not EGRI.

## Formula

```
high_risk iff hypoxemia or extremes_of_size or anatomic_challenges or vomit_blood_fluid or exsanguination or neck_mobility_limited; low_risk iff not high_risk; criteria_met is the count of those six flags that are true (Davis 2017 HEAVEN; high_risk iff any of six caller-assigned flags)
```

## Citation

[HEAVEN Criteria: Derivation of a New Difficult Airway Prediction Tool](https://doi.org/10.1016/j.amj.2017.04.001)
Davis DP, Olvera DJ
Air Med J. 2017;36(4):195-197
DOI: [10.1016/j.amj.2017.04.001](https://doi.org/10.1016/j.amj.2017.04.001)

## Worked example

### All six flags false (low_risk, criteria_met 0)

Given: `anatomic_challenges=false, exsanguination=false, extremes_of_size=false, hypoxemia=false, neck_mobility_limited=false, vomit_blood_fluid=false`

1. hypoxemia false
2. extremes_of_size false
3. anatomic_challenges false
4. vomit_blood_fluid false
5. exsanguination false
6. neck_mobility_limited false
7. high_risk_any is false; high_risk is false; low_risk is true; criteria_met is 0


### Hypoxemia only (high_risk, criteria_met 1)

Given: `anatomic_challenges=false, exsanguination=false, extremes_of_size=false, hypoxemia=true, neck_mobility_limited=false, vomit_blood_fluid=false`

1. hypoxemia true is a HEAVEN flag
2. The other five flags are false
3. high_risk_any is true; high_risk is true; low_risk is false; criteria_met is 1


### All six flags true (high_risk, criteria_met 6)

Given: `anatomic_challenges=true, exsanguination=true, extremes_of_size=true, hypoxemia=true, neck_mobility_limited=true, vomit_blood_fluid=true`

1. Each of the six flags is true
2. high_risk_any is true; high_risk is true; low_risk is false; criteria_met is 6


## Also searched as

- HEAVEN criteria
- HEAVEN airway
- Davis 2017 HEAVEN
- difficult airway HEAVEN
- first-attempt intubation failure
- air medical HEAVEN criteria
- HEAVEN RSI
- difficult laryngoscopy HEAVEN

## Parameters

- `hypoxemia` (boolean, required): Hypoxemia (SpO2 ≤93% at initial laryngoscopy) as assigned by the caller (Davis 2017). true is a HEAVEN flag. magent does not measure SpO2.
- `extremes_of_size` (boolean, required): Extremes of size (pediatric ≤8 years or clinical obesity) as assigned by the caller (Davis 2017). true is a HEAVEN flag. magent does not examine the patient or assign age.
- `anatomic_challenges` (boolean, required): Anatomic challenges that limit laryngoscopy as assigned by the caller (Davis 2017). true is a HEAVEN flag. magent does not examine the airway.
- `vomit_blood_fluid` (boolean, required): Vomit, blood, or fluid in the pharynx or hypopharynx as assigned by the caller (Davis 2017). true is a HEAVEN flag. magent does not examine the airway.
- `exsanguination` (boolean, required): Exsanguination (suspected anemia that would accelerate desaturation) as assigned by the caller (Davis 2017). true is a HEAVEN flag. magent does not assay hemoglobin.
- `neck_mobility_limited` (boolean, required): Limited neck mobility as assigned by the caller (Davis 2017). true is a HEAVEN flag. magent does not examine the neck.

## 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/heaven`
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": [
    {
      "anatomic_challenges": "false",
      "exsanguination": "false",
      "extremes_of_size": "false",
      "hypoxemia": "false",
      "neck_mobility_limited": "false",
      "vomit_blood_fluid": "false"
    },
    {
      "anatomic_challenges": "false",
      "exsanguination": "false",
      "extremes_of_size": "false",
      "hypoxemia": "false",
      "neck_mobility_limited": "false",
      "vomit_blood_fluid": "false"
    }
  ]
}
```

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

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/heaven",
  "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": "Davis DP, Olvera DJ",
        "doi": "10.1016/j.amj.2017.04.001",
        "id": "davis-2017",
        "pmid": "28739243",
        "source": "Air Med J. 2017;36(4):195-197",
        "title": "HEAVEN Criteria: Derivation of a New Difficult Airway Prediction Tool"
      },
      "formula": "heaven",
      "formula_expression": "high_risk iff hypoxemia or extremes_of_size or anatomic_challenges or vomit_blood_fluid or exsanguination or neck_mobility_limited; low_risk iff not high_risk; criteria_met is the count of those six flags that are true (Davis 2017 HEAVEN; high_risk iff any of six caller-assigned flags)",
      "criteria": [
        {
          "factor": "hypoxemia",
          "met": false
        },
        {
          "factor": "extremes_of_size",
          "met": false
        },
        {
          "factor": "anatomic_challenges",
          "met": false
        },
        {
          "factor": "vomit_blood_fluid",
          "met": false
        },
        {
          "factor": "exsanguination",
          "met": false
        },
        {
          "factor": "neck_mobility_limited",
          "met": false
        },
        {
          "factor": "high_risk_any",
          "met": false
        }
      ],
      "high_risk": false,
      "low_risk": true,
      "criteria_met": 0
    },
    {
      "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": "Davis DP, Olvera DJ",
        "doi": "10.1016/j.amj.2017.04.001",
        "id": "davis-2017",
        "pmid": "28739243",
        "source": "Air Med J. 2017;36(4):195-197",
        "title": "HEAVEN Criteria: Derivation of a New Difficult Airway Prediction Tool"
      },
      "formula": "heaven",
      "formula_expression": "high_risk iff hypoxemia or extremes_of_size or anatomic_challenges or vomit_blood_fluid or exsanguination or neck_mobility_limited; low_risk iff not high_risk; criteria_met is the count of those six flags that are true (Davis 2017 HEAVEN; high_risk iff any of six caller-assigned flags)",
      "criteria": [
        {
          "factor": "hypoxemia",
          "met": false
        },
        {
          "factor": "extremes_of_size",
          "met": false
        },
        {
          "factor": "anatomic_challenges",
          "met": false
        },
        {
          "factor": "vomit_blood_fluid",
          "met": false
        },
        {
          "factor": "exsanguination",
          "met": false
        },
        {
          "factor": "neck_mobility_limited",
          "met": false
        },
        {
          "factor": "high_risk_any",
          "met": false
        }
      ],
      "high_risk": false,
      "low_risk": true,
      "criteria_met": 0
    }
  ]
}
```

## Response fields

- `formula` (string): heaven
- `formula_expression` (string): Davis 2017 HEAVEN: high_risk if any of the six caller-assigned flags; criteria_met is the count of true flags (0-6)
- `high_risk` (boolean): true iff any of the six flags is true. Derivation: all failed first-attempt patients had ≥1 HEAVEN criterion. Not an intubation order.
- `low_risk` (boolean): true iff none of the six flags is true (not high_risk)
- `criteria_met` (integer): Count of the six HEAVEN flags that are true (0-6)
- `criteria` (array): Per-flag rows plus high_risk_any (met iff any of the six flags is true)
- `citation` (object): Davis 2017 Air Med J citation
- `disclaimer` (string): Not-a-device notice

## Example JSON

Frozen fixture. Not a live lookup.

```json
{
  "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": "Davis DP, Olvera DJ",
    "doi": "10.1016/j.amj.2017.04.001",
    "id": "davis-2017",
    "pmid": "28739243",
    "source": "Air Med J. 2017;36(4):195-197",
    "title": "HEAVEN Criteria: Derivation of a New Difficult Airway Prediction Tool"
  },
  "formula": "heaven",
  "formula_expression": "high_risk iff hypoxemia or extremes_of_size or anatomic_challenges or vomit_blood_fluid or exsanguination or neck_mobility_limited; low_risk iff not high_risk; criteria_met is the count of those six flags that are true (Davis 2017 HEAVEN; high_risk iff any of six caller-assigned flags)",
  "criteria": [
    {
      "factor": "hypoxemia",
      "met": false
    },
    {
      "factor": "extremes_of_size",
      "met": false
    },
    {
      "factor": "anatomic_challenges",
      "met": false
    },
    {
      "factor": "vomit_blood_fluid",
      "met": false
    },
    {
      "factor": "exsanguination",
      "met": false
    },
    {
      "factor": "neck_mobility_limited",
      "met": false
    },
    {
      "factor": "high_risk_any",
      "met": false
    }
  ],
  "high_risk": false,
  "low_risk": true,
  "criteria_met": 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

- [Mallampati](https://magentlab.com/docs/mallampati) — Return the Samsoon 1987 modified Mallampati class 1-4 from a caller-assigned integer, with a stable label.
- [EGRI](https://magentlab.com/docs/egri) — Sum the El-Ganzouri 1996 simplified airway risk index (seven 0/1/2 items; max 12) and return high_risk when the score is 4 or more.
- [Aldrete](https://magentlab.com/docs/aldrete) — Compute the Aldrete 1970 postanesthetic recovery score as the sum of five caller-assigned 0-2 signs (activity, respiration, circulation, consciousness, color) and return the 1970 recovery-room 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.

- 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.