# GCS-Pupils score

GCS-Pupils

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

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

## What it computes

Return the Brennan 2018 GCS-Pupils index as caller-assigned total GCS 3-15 minus pupil reactivity score (unreactive pupils 0, 1, or 2).

## When to use

When an agent already has a 1976-style total GCS 3-15 and a pupil reactivity score (0-2) and needs the published GCS-P index, not eye/verbal/motor components and not Part 2 outcome charts.

## When not to use

- Not a medical device and not a diagnosis of TBI severity as a device output.
- magent does not examine pupils or assign GCS. It uses caller-assigned total GCS 3-15 (1976-style total) minus PRS.
- Does not compute eye, verbal, or motor components (use /api/calc/gcs).
- Does not implement Brennan 2018 Part 2 probability charts. Returns the GCS-P index only.

## Formula

```
GCS-P = GCS - PRS; PRS is the number of unreactive pupils (0, 1, or 2); GCS 3-15; GCS-P range 1-15 (Brennan 2018)
```

## Citation

[Simplifying the use of prognostic information in traumatic brain injury. Part 1: The GCS-Pupils score: an extended index of clinical severity](https://doi.org/10.3171/2017.12.JNS172780)
Brennan PM, Murray GD, Teasdale GM
J Neurosurg. 2018;128(6):1612-1620
DOI: [10.3171/2017.12.JNS172780](https://doi.org/10.3171/2017.12.JNS172780)

## Worked example

### GCS 15, both pupils reactive

Given: `gcs=15, unreactive_pupils=0`

1. PRS (unreactive_pupils) = 0
2. GCS-P = 15 - 0 = 15


## Also searched as

- GCS-P
- GCS pupils
- pupil reactivity score
- GCS-Pupils score
- Brennan GCS-P
- unreactive pupils GCS
- GCS minus PRS
- pupil reactivity score GCS

## Parameters

- `gcs` (integer, required): Caller-assigned total GCS as an integer 3-15 (1976-style total). magent does not assign GCS and does not take eye, verbal, or motor here (use /api/calc/gcs).
- `unreactive_pupils` (integer, required): Pupil reactivity score (PRS): integer 0, 1, or 2. 0 both pupils reactive, 1 one unreactive, 2 both unreactive. magent does not examine pupils.

## 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/gcs_pupils`
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": [
    {
      "gcs": "15",
      "unreactive_pupils": "0"
    },
    {
      "gcs": "15",
      "unreactive_pupils": "0"
    }
  ]
}
```

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

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/gcs_pupils",
  "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": "Brennan PM, Murray GD, Teasdale GM",
        "doi": "10.3171/2017.12.JNS172780",
        "id": "brennan-2018",
        "pmid": "29631516",
        "source": "J Neurosurg. 2018;128(6):1612-1620",
        "title": "Simplifying the use of prognostic information in traumatic brain injury. Part 1: The GCS-Pupils score: an extended index of clinical severity"
      },
      "formula": "gcs_pupils",
      "formula_expression": "GCS-P = GCS - PRS; PRS is the number of unreactive pupils (0, 1, or 2); GCS 3-15; GCS-P range 1-15 (Brennan 2018)",
      "gcs": 15,
      "gcs_p": 15,
      "pupil_reactivity_score": 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": "Brennan PM, Murray GD, Teasdale GM",
        "doi": "10.3171/2017.12.JNS172780",
        "id": "brennan-2018",
        "pmid": "29631516",
        "source": "J Neurosurg. 2018;128(6):1612-1620",
        "title": "Simplifying the use of prognostic information in traumatic brain injury. Part 1: The GCS-Pupils score: an extended index of clinical severity"
      },
      "formula": "gcs_pupils",
      "formula_expression": "GCS-P = GCS - PRS; PRS is the number of unreactive pupils (0, 1, or 2); GCS 3-15; GCS-P range 1-15 (Brennan 2018)",
      "gcs": 15,
      "gcs_p": 15,
      "pupil_reactivity_score": 0
    }
  ]
}
```

## Response fields

- `formula` (string): gcs_pupils
- `formula_expression` (string): Exact expression used
- `gcs` (integer): Caller-assigned total GCS 3-15
- `pupil_reactivity_score` (integer): PRS: unreactive pupils 0, 1, or 2
- `gcs_p` (integer): GCS minus PRS (range 1-15). Index only.
- `citation` (object): Brennan 2018 J Neurosurg 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": "Brennan PM, Murray GD, Teasdale GM",
    "doi": "10.3171/2017.12.JNS172780",
    "id": "brennan-2018",
    "pmid": "29631516",
    "source": "J Neurosurg. 2018;128(6):1612-1620",
    "title": "Simplifying the use of prognostic information in traumatic brain injury. Part 1: The GCS-Pupils score: an extended index of clinical severity"
  },
  "formula": "gcs_pupils",
  "formula_expression": "GCS-P = GCS - PRS; PRS is the number of unreactive pupils (0, 1, or 2); GCS 3-15; GCS-P range 1-15 (Brennan 2018)",
  "gcs": 15,
  "gcs_p": 15,
  "pupil_reactivity_score": 0
}
```

## Errors

- HTTP 400 `invalid_gcs_total`: gcs must be an integer from 3 to 15. Returned before settlement; you are not charged.
- HTTP 400 `invalid_unreactive_pupils`: unreactive_pupils must be an integer 0, 1, or 2 (Brennan 2018 pupil reactivity score). 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

- [Glasgow Coma Scale](https://magentlab.com/docs/gcs) — Compute the Glasgow Coma Scale as the sum of caller-assigned eye, verbal, and motor integers. The 1974 or 1976 edition is required.
- [FOUR score](https://magentlab.com/docs/four-score) — Compute the FOUR score as the sum of caller-assigned eye, motor, brainstem, and respiration integers 0-4.

## 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.