{
  "patients": {
    "description": "Patient demographic information",
    "columns": {
      "subject_id": "Unique patient identifier",
      "gender": "Biological sex",
      "anchor_age": "Approximate age",
      "anchor_year": "Anchor year for age"
    }
  },
  "admissions": {
    "description": "Hospital admissions for patients",
    "columns": {
      "hadm_id": "Hospital admission ID",
      "subject_id": "Patient ID",
      "admittime": "Admission timestamp",
      "dischtime": "Discharge timestamp",
      "admission_type": "Emergency, elective, etc",
      "admission_location": "Source of admission"
    }
  },
  "icustays": {
    "description": "ICU stay records",
    "columns": {
      "stay_id": "ICU stay identifier",
      "hadm_id": "Hospital admission ID",
      "subject_id": "Patient ID",
      "intime": "ICU admission time",
      "outtime": "ICU discharge time"
    }
  },
  "chartevents": {
    "description": "Time-series ICU measurements (vitals, labs)",
    "columns": {
      "stay_id": "ICU stay ID",
      "itemid": "Measurement type",
      "charttime": "Time of observation",
      "valuenum": "Numeric value"
    }
  },
  "diagnoses_icd": {
    "description": "ICD diagnoses for admissions",
    "columns": {
      "hadm_id": "Hospital admission ID",
      "icd_code": "Diagnosis code",
      "icd_version": "ICD version"
    }
  }
}