Agent Service · x402 · early usage

Ottawa knee rule (Stiell 1995)

by api.magentlab.com · discovered, not yet claimed by its owner · updated 2026-10-13

30d calls5

30d payers2

MethodPOST

Outputjson

Mirrored from Coinbase's public x402 Bazaar. The description is the provider's own text and has not been reviewed here; the payment requirements are copied as published.

What it does

Ottawa knee rule (Stiell 1995). Knee x-ray is indicated when any of: age 55 or older, bone tenderness at the fibular head, isolated patellar tenderness (caller-applied), inability to flex to 90 degrees, or inability to bear weight both immediately after injury and in the emergency department (four steps). One weight-bearing failure alone is not enough. Not a diagnosis of fracture, not the Ottawa ankle or foot rule, and not the Pittsburgh knee rule. magent does not examine the knee.

Tags: ottawa-knee · knee · radiography · emergency · calculator · bazaar

Call contract

Method: POST
Input: HTTP request
Output: json
Last paid call: 2026-10-13

Input example from Bazaar metadata

{
  "items": [
    {
      "age": 40,
      "fibular_head_tenderness": false,
      "flexion_less_than_90": false,
      "isolated_patellar_tenderness": false,
      "unable_to_bear_weight_immediately": false,
      "unable_to_bear_weight_in_ed": false
    },
    {
      "age": 40,
      "fibular_head_tenderness": false,
      "flexion_less_than_90": false,
      "isolated_patellar_tenderness": false,
      "unable_to_bear_weight_immediately": false,
      "unable_to_bear_weight_in_ed": false
    }
  ]
}

Output example

{
  "count": 2,
  "items": [
    {
      "age_years": 40,
      "citation": {
        "authors": "Stiell IG, Greenberg GH, Wells GA, et al.",
        "doi": "10.1016/S0196-0644(95)70106-0",
        "id": "stiell-1995",
        "source": "Ann Emerg Med. 1995;26(4):405-413",
        "title": "Derivation of a decision rule for the use of radiography in acute knee injuries"
      },
      "criteria": [
        {
          "factor": "age_ge_55",
          "met": false,
          "value": 40
        },
        {
          "factor": "fibular_head_tenderness",
          "met": false
        },
        {
          "factor": "isolated_patellar_tenderness",
          "met": false
        },
        {
          "factor": "flexion_less_than_90",
          "met": false
        },
        {
          "factor": "unable_to_bear_weight_both",
          "met": false,
          "unable_to_bear_weight_immediately": false,
          "unable_to_bear_weight_in_ed": false
        }
      ],
      "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.",
      "formula": "ottawa_knee",
      "formula_expression": "Knee x-ray indicated iff age >= 55 or fibular_head_tenderness or isolated_patellar_tenderness or flexion_less_than_90 or (unable_to_bear_weight_immediately and unable_to_bear_weight_in_ed)",
      "xray_indicated": false
    },
    {
      "age_years": 40,
      "citation": {
        "authors": "Stiell IG, Greenberg GH, Wells GA, et al.",
        "doi": "10.1016/S0196-0644(95)70106-0",
        "id": "stiell-1995",
        "source": "Ann Emerg Med. 1995;26(4):405-413",
        "title": "Derivation of a decision rule for the use of radiography in acute knee injuries"
      },
      "criteria": [
        {
          "factor": "age_ge_55",
          "met": false,
          "value": 40
        },
        {
          "factor": "fibular_head_tenderness",
          "met": false
        },
        {
          "factor": "isolated_patellar_tenderness",
          "met": false
        },
        {
          "factor": "flexion_less_than_90",
          "met": false
        },
        {
          "factor": "unable_to_bear_weight_both",
          "met": false,
          "unable_to_bear_weight_immediately": false,
          "unable_to_bear_weight_in_ed": false
        }
      ],
      "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.",
      "formula": "ottawa_knee",
      "formula_expression": "Knee x-ray indicated iff age >= 55 or fibular_head_tenderness or isolated_patellar_tenderness or flexion_less_than_90 or (unable_to_bear_weight_immediately and unable_to_bear_weight_in_ed)",
      "xray_indicated": false
    }
  ],
  "path": "/api/calc/ottawa_knee"
}

Use with an agent

Discover. Agents find this listing with GET https://bazaar.saylorinnovations.com/discovery/search?query=…, the MCP tool search_resources, or /discovery/resources.
Inspect. Fetch /resources/38987.json for the price and payment options.
Pay. Call GET https://api.magentlab.com/api/calc/ottawa_knee. The provider answers 402 with its payment requirements. An x402 client signs one of the options below and retries with PAYMENT-SIGNATURE.
Execute. The provider returns 200 with the data. Agent Bazaar is not in the request path and never sees your payment.

For humans

You don't need an account or an API key; you need a wallet holding a small amount of USDC on Base, and an x402-capable client (see the examples below). Call the endpoint unpaid first to see exactly what it asks for.

Pricing & payment

Price: $0.005 / request
Protocol: x402 v2
Auth: No account or API key. Pay per request.
Networks: Base
Demand: 5 calls · 2 unique payers in 30d (public x402 Bazaar data)

x402 payment requirements

Scheme	Network	Asset	Amount	Pay to	Timeout
exact	Base eip155:8453	USDC	$0.005	0x836Be278f1739fB4308091cD1852F7971Bc19Ee2	600s

accepts[] (raw JSON)

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x836Be278f1739fB4308091cD1852F7971Bc19Ee2",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "5000",
    "amountUsd": 0.005,
    "maxTimeoutSeconds": 600
  }
]

Schemas

Output schema (JSON Schema)

{
  "properties": {
    "example": {
      "type": "object"
    },
    "type": {
      "type": "string"
    }
  },
  "required": [
    "type"
  ],
  "type": "object"
}

Example shape — generated from the schema, not a captured live response

{
  "example": {},
  "type": "string"
}

Examples

curl

curl "https://api.magentlab.com/api/calc/ottawa_knee"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

JavaScript

const res = await fetch("https://api.magentlab.com/api/calc/ottawa_knee");
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

Python

import httpx
res = httpx.get("https://api.magentlab.com/api/calc/ottawa_knee")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header

Details

Provider: api.magentlab.com
Endpoint: https://api.magentlab.com/api/calc/ottawa_knee
Machine-readable: /resources/38987.json