# NEXUS Head CT Rule Calculator (Mower 2017)

> NEXUS Head CT Rule Calculator (Mower 2017) is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14).

Applies the NEXUS Head CT instrument to determine whether a head CT may be safely omitted based on eight clinical criteria

## Facts

- Endpoint: GET https://api.magentlab.com/api/calc/nexus_head_ct
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/nexus-head-ct-rule-calculator-mower-2017-e5001188
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_KWrvxylHQnh_Ga9M61XI-

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability nexus-head-ct-rule-calculator-mower-2017-e5001188
```

Example prompt: Run the NEXUS Head CT rule on a 58-year-old patient with no skull fracture, no scalp hematoma, no neurologic deficit, alert and behaving normally, no coagulopathy, and no persistent vomiting — tell me if head CT can be omitted.

## When to prefer this

Use this endpoint when you need to apply the Mower 2017 NEXUS Head CT rule specifically — not the Canadian CT Head Rule and not the Hoffman 2000 NEXUS C-spine rule. Prefer it when all eight criterion flags have already been clinically assessed by a provider and you need a programmatic low-risk determination for documentation, decision support, or workflow automation.

## Known failure modes

- Missing required query parameters returns a validation error
- Age outside integer range 18–120 may be rejected
- Non-boolean values for flag parameters cause schema validation failure
- Caller-assigned findings reflect the provider's clinical assessment; the API does not validate clinical plausibility

## How this service works

NEXUS Head CT (Mower 2017). Low-risk, and CT may be omitted by this instrument, only when all eight are absent: age 65 or older, evidence of skull fracture, scalp hematoma, neurologic deficit, altered alertness, abnormal behavior, coagulopathy, and persistent vomiting. Age 65 is high-risk; age 64 is not on age alone. Not a diagnosis, not a CT order, not Hoffman 2000 NEXUS C-spine, and not the Canadian CT Head Rule. magent does not examine the patient.

## Output

Returns a low-risk flag (true/false) indicating whether all eight NEXUS Head CT criteria are absent (true = low-risk, CT may be omitted), along with the status of each individual criterion that triggered or cleared the rule.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "headers": {
     "type": "object",
     "additionalProperties": {
      "type": "string"
     }
    },
    "queryParams": {
     "type": "object",
     "required": [
      "age",
      "skull_fracture",
      "scalp_hematoma",
      "neurologic_deficit",
      "altered_alertness",
      "abnormal_behavior",
      "coagulopathy",
      "persistent_vomiting"
     ],
     "properties": {
      "age": {
       "type": "integer",
       "description": "Age in years (integer 18-120). Age ≥ 65 is a high-risk criterion; 64 is not high-risk on age alone. Low-risk age criterion holds when age < 65."
      },
      "coagulopathy": {
       "type": "boolean",
       "description": "Coagulopathy as assigned by the caller. true means coagulopathy is present and low_risk is false. true or false. magent does not interpret a coagulation assay."
      },
      "scalp_hematoma": {
       "type": "boolean",
       "description": "Scalp hematoma as assigned by the caller. true means a scalp hematoma is present and low_risk is false. true or false. magent does not examine the scalp."
      },
      "skull_fracture": {
       "type": "boolean",
       "description": "Evidence of skull fracture as assigned by the caller. true means a skull-fracture finding is present and low_risk is false. true or false. magent does not examine the patient or read a radiograph."
      },
      "abnormal_behavior": {
       "type": "boolean",
       "description": "Abnormal behavior as assigned by the caller. true means abnormal behavior is present and low_risk is false. true or false. magent does not examine the patient."
      },
      "altered_alertness": {
       "type": "boolean",
       "description": "Altered level of alertness as assigned by the caller. true means alertness is altered and low_risk is false. true or false. magent does not assign GCS."
      },
      "neurologic_deficit": {
       "type": "boolean",
       "description": "Neurologic deficit (neurosurgical deficits) as assigned by the caller. true means a deficit is present and low_risk is false. true or false. magent does no
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/nexus-head-ct-rule-calculator-mower-2017-e5001188/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.magentlab.com](https://www.zero.xyz/host/api.magentlab.com/llms.txt)