{
  "schema_id": "FloodExtentChange",
  "version": "0.1",
  "description": "Detect new standing water — river overflow, inundated fields, lake expansion — between before/after Sentinel-2 tiles.",
  "class_match": "FL",
  "bands_required": ["B03", "B08", "B11"],
  "band_rationale": "MNDWI (Green - SWIR1) and NDWI (Green - NIR) enhance water contrast; visible RGB provides context.",
  "predicate": "Has new standing water appeared or existing water expanded between the before and after tiles (river overflow, flooded fields, lake expansion, coastal inundation)?",
  "fields": {
    "severity": {"type": "enum", "values": ["low", "moderate", "high", "extreme"]},
    "area_fraction": {"type": "number", "range": [0.0, 1.0]},
    "source": {"type": "enum", "values": ["river_overflow", "coastal", "lake_expansion", "field_inundation", "unknown"]},
    "vlm_explanation": {"type": "string"},
    "confidence": {"type": "number", "range": [0.0, 1.0]}
  },
  "negative_output": null,
  "negative_instruction": "If no new water or water expansion is visible, return null."
}