# CATCH Pediatric Head Injury CT Decision Rule > CATCH Pediatric Head Injury CT Decision Rule 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 CATCH (2010) clinical decision rule to determine if CT is indicated after pediatric minor head injury, returning high/medium/low risk classification based on 7 caller-assigned findings. ## Facts - Endpoint: GET https://api.magentlab.com/api/calc/catch - 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/catch-pediatric-head-injury-ct-decision-rule-996a2e23 - Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ij7uTTRkjdjJ-VhIj2zuJ 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 catch-pediatric-head-injury-ct-decision-rule-996a2e23 ``` Example prompt: Apply the CATCH rule for a child who had a minor head injury: GCS was less than 15 at 2 hours (true), no suspected open or depressed skull fracture (false), worsening headache is present (true), no irritability (false), no basal skull fracture signs (false), no large boggy scalp hematoma (false), and the mechanism was a fall from a bicycle with no helmet — so dangerous mechanism is true. ## When to prefer this Use this endpoint when you need to apply the specific CATCH (Osmond 2010) clinical decision rule for pediatric minor head injury CT triage, and you already have all 7 findings assigned by a qualified clinician. Prefer this over PECARN, CHALICE, Canadian CT Head, NEXUS, or CATCH-2 endpoints when the clinical team has standardized on the original CATCH rule. This is a pure computation endpoint — it does not replace clinical judgment and is not a medical device. ## Known failure modes - Missing any of the 7 required boolean query parameters returns a validation error - Non-boolean values for any flag cause a schema validation failure - Payment failure (x402) if USDC not provided or insufficient - Network timeout if the API is temporarily unavailable ## How this service works CATCH (Osmond 2010). CT indicated if any of 7 caller-assigned findings after pediatric minor head injury. High (neurologic intervention): GCS <15 at 2h, open/depressed skull fracture, worsening headache, irritability. Medium if not high (brain injury on CT): basal skull fracture, large boggy scalp hematoma, dangerous mechanism. Low if none. Not PECARN, CHALICE, Canadian CT Head, NEXUS, or CATCH-2. magent does not examine the child or read CT. Not a diagnosis or medical device. ## Output Returns a CATCH risk classification — high (neurologic intervention risk, CT indicated), medium (brain injury on CT risk, CT indicated), or low (no high or medium findings, CT not indicated by this rule alone) — based on the 7 boolean flags provided by the caller. The endpoint does not examine the patient or read imaging; all inputs are caller-assigned. ## 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": [ "gcs_lt_15_at_2h", "suspected_open_or_depressed_skull_fracture", "worsening_headache", "irritability", "basal_skull_fracture", "large_boggy_scalp_hematoma", "dangerous_mechanism" ], "properties": { "irritability": { "type": "boolean", "description": "Irritability on examination. true or false as assigned by the caller. High-risk (need for neurologic intervention). magent does not examine the child." }, "gcs_lt_15_at_2h": { "type": "boolean", "description": "GCS score <15 at two hours after injury. true or false as assigned by the caller. High-risk (need for neurologic intervention). magent does not take a GCS integer." }, "worsening_headache": { "type": "boolean", "description": "History of worsening headache. true or false as assigned by the caller. High-risk (need for neurologic intervention)." }, "dangerous_mechanism": { "type": "boolean", "description": "Dangerous mechanism of injury as assigned by the caller. true or false. Medium-risk (brain injury on CT). Paper examples: motor vehicle collision, fall from elevation ≥3 ft / ≥91 cm or 5 stairs, fall from bicycle with no helmet. magent does not classify mechanism." }, "basal_skull_fracture": { "type": "boolean", "description": "Any sign of basal skull fracture. true or false as assigned by the caller. Medium-risk (brain injury on CT). magent does not examine the child." }, "large_boggy_scalp_hematoma": { "type": "boolean", "description": "Large, boggy hematoma of the scalp. true or false as assigned by the caller. Medium-risk (brain injury on CT). magent does not examine the child." }, "suspected_open_or_depressed_skull_fracture": { "type": "boolean", "description": "Suspected open or depressed skull fracture. true … (truncated) ``` ## Response schema (JSON Schema) ```json { "type": "json", "example": { "path": "/api/calc/catch", "count": 2, "items": [ { "formula": "catch", "citation": { "id": "osmond-2010", "doi": "10.1503/cmaj.091421", "pmid": "20142371", "title": "CATCH: a clinical decision rule for the use of computed tomography in children with minor head injury", "source": "CMAJ. 2010;182(4):341-348", "authors": "Osmond MH, Klassen TP, Wells GA, et al." }, "criteria": [ { "met": false, "factor": "gcs_lt_15_at_2h" }, { "met": false, "factor": "suspected_open_or_depressed_skull_fracture" }, { "met": false, "factor": "worsening_headache" }, { "met": false, "factor": "irritability" }, { "met": false, "factor": "basal_skull_fracture" }, { "met": false, "factor": "large_boggy_scalp_hematoma" }, { "met": false, "factor": "dangerous_mechanism" } ], "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.", "ct_indicated": false, "catch_low_risk": true, "catch_high_risk": false, "catch_medium_risk": false, "formula_expression": "high if any of gcs_lt_15_at_2h, suspected_open_or_depressed_skull_fracture, worsening_headache, irritability; else medium if any of basal_skull_fracture, large_boggy_scalp_hematoma, dangerous_mechanism; else low; CT indicated if high or medium" }, { "formula": "catch", "citation": { "id": "osmond-2010", "doi": "10.1503/cmaj.091421", "pmid": "20142371", "title": "CATCH: a clinical decision rule for the use of computed tomography in children with minor head injury", "source": "CMAJ. 2010;182(4):341-348", "authors": "Osmond MH, Klassen TP, Wells GA, et al." }, "criteria": [ { "met": false, "factor": "gcs_lt_15_at_2h" }, { "met": false, "factor": "suspected_open_or_depressed_skull_fracture" }, { "met": false, "factor": "worsening_headache" }, { "met": false, "factor": "irritability" }, { "met": false, "factor": "basal_skull_fracture" }, { "met": false, "factor": "large_boggy_scalp_hematoma" }, { "met": false, "factor": "dangerous_mecha … (truncated) ``` ## More - Live health (JSON, refreshed every minute): https://www.zero.xyz/c/catch-pediatric-head-injury-ct-decision-rule-996a2e23/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)