# CHALICE Pediatric Head CT Decision Rule (magent) > CHALICE Pediatric Head CT Decision Rule (magent) is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15). Applies the CHALICE clinical decision rule to determine if CT imaging is required for a child (ages 0–15) following a head injury ## Facts - Endpoint: GET https://api.magentlab.com/api/calc/chalice - Price: $0.005/call - Payment: x402 - Status: unknown - Last checked: 2026-09-15 - Activations on Zero: 0 - Tags: x402 - Canonical page: https://www.zero.xyz/c/chalice-pediatric-head-ct-decision-rule-magent-afcdcdca - Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_RAmLfmRFF6TzQy9nih2Ui 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 chalice-pediatric-head-ct-decision-rule-magent-afcdcdca ``` Example prompt: Using the CHALICE rule, does a 4-year-old with a GCS of 13 need a CT after falling about 4 meters? No vomiting, no loss of consciousness, no seizure, no amnesia, no NAI suspicion, no focal neurology, no skull signs, no projectile, no high-speed RTA. ## When to prefer this Use this endpoint when you need to apply the CHALICE (Dunning 2006) clinical decision rule specifically, for a patient aged 0–15 after a head injury, and your caller has already assessed and categorised the clinical flags. Prefer this over PECARN or CATCH when the clinical workflow specifies CHALICE. It is not a substitute for clinical examination and cannot examine the patient. ## Known failure modes - Age 16 or above is rejected — CHALICE applies only to children under 16 - Invalid GCS values outside 3–15 range will be rejected - Missing required boolean flags will cause a validation error - Caller-assigned flags (NAI, mechanism) may reflect inaccurate history — garbage in, garbage out - Does not replace clinical judgment; result is a calculation aid, not a diagnosis ## How this service works CHALICE (Dunning 2006). CT required in children 0-15 if any history, exam, or mechanism criterion is present; else low risk. GCS <14, or GCS <15 if age <1 year. Bruise/swelling/laceration >5 cm only if age <1 year. Mechanism is caller-assigned (paper: high-speed RTA >40 mph as occupant/pedestrian/cyclist; fall >3 m; high-speed projectile or object). NAI is caller-assigned. Not PECARN, CATCH, or Canadian CT Head. magent does not examine the child. Not a diagnosis or medical device. ## Output Returns a CHALICE rule result indicating whether CT is required or the child is low risk, based on which history, examination, or mechanism criteria are present. Identifies which specific criterion triggered the CT recommendation, if any. ## 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", "gcs", "loc_gt_5_min", "amnesia_gt_5_min", "abnormal_drowsiness", "vomits_ge_3", "suspicion_nai", "seizure_no_epilepsy", "penetrating_depressed_or_tense_fontanelle", "basal_skull_fracture", "focal_neurology", "bruise_swelling_laceration_gt_5cm", "high_speed_rta", "fall_gt_3m", "high_speed_projectile_or_object" ], "properties": { "age": { "type": "integer", "description": "Age in whole years (0-15). CHALICE is for children younger than 16. Age 0 is younger than 1 year (GCS <15 and bruise >5 cm apply). Age 1-15 uses GCS <14. Age 16 is rejected." }, "gcs": { "type": "integer", "description": "Glasgow Coma Scale total, integer 3-15 as assigned by the caller. Examination criterion: GCS <14, or GCS <15 if age <1 year." }, "fall_gt_3m": { "type": "boolean", "description": "Fall >3 m as assigned by the caller. true or false. Mechanism criterion. magent does not classify mechanism or take a height integer." }, "vomits_ge_3": { "type": "boolean", "description": "Three or more vomits after the head injury. true or false as assigned by the caller. History criterion." }, "loc_gt_5_min": { "type": "boolean", "description": "Witnessed loss of consciousness >5 minutes. true or false as assigned by the caller. History criterion. magent does not take a duration integer." }, "suspicion_nai": { "type": "boolean", "description": "Suspicion of non-accidental injury as assigned by the caller. true or false. History criterion. magent does not diagnose NAI." }, "high_speed_rta": { "type": "boolean", "description": "High-speed road traffic accident as occupant, pedestrian, or cyclist as assigned by the caller (paper: speed >40 mph). true or … (truncated) ``` ## Response schema (JSON Schema) ```json { "type": "json", "example": { "path": "/api/calc/chalice", "count": 2, "items": [ { "gcs": 15, "formula": "chalice", "citation": { "id": "dunning-2006", "doi": "10.1136/adc.2005.083980", "pmid": "17056862", "title": "Derivation of the children's head injury algorithm for the prediction of important clinical events decision rule for head injury in children", "source": "Arch Dis Child. 2006;91(11):885-891", "authors": "Dunning J, Daly JP, Lomas JP, Lecky F, Batchelor J, Mackway-Jones K" }, "criteria": [ { "met": false, "factor": "loc_gt_5_min" }, { "met": false, "factor": "amnesia_gt_5_min" }, { "met": false, "factor": "abnormal_drowsiness" }, { "met": false, "factor": "vomits_ge_3" }, { "met": false, "factor": "suspicion_nai" }, { "met": false, "factor": "seizure_no_epilepsy" }, { "met": false, "value": 15, "factor": "gcs_criterion" }, { "met": false, "factor": "penetrating_depressed_or_tense_fontanelle" }, { "met": false, "factor": "basal_skull_fracture" }, { "met": false, "factor": "focal_neurology" }, { "met": false, "value": 10, "factor": "bruise_swelling_laceration_gt_5cm" }, { "met": false, "factor": "high_speed_rta" }, { "met": false, "factor": "fall_gt_3m" }, { "met": false, "factor": "high_speed_projectile_or_object" } ], "age_years": 10, "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.", "chalice_low_risk": true, "formula_expression": "CT required if any history, examination, or mechanism criterion is present; else low risk. GCS <14, or GCS <15 if age <1 year. Bruise, swelling, or laceration >5 cm only if age <1 year. Mechanism is caller-assigned.", "chalice_ct_required": false }, { "gcs": 15, "formula": "chalice", "citation": { "id": "dunning-2006", "doi": "10.1136/adc.2005.083980", "pmid": "17056862", "title": "Derivation of the children's head injury algorithm for the prediction of important clinical events decision rule for head injury in children", "sour … (truncated) ``` ## More - Live health (JSON, refreshed every minute): https://www.zero.xyz/c/chalice-pediatric-head-ct-decision-rule-magent-afcdcdca/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)