{
  "schema_id": "UrbanChangeDelta",
  "version": "0.1",
  "description": "Detect new buildings, roads, or other built-up features appearing between before/after Sentinel-2 tiles.",
  "class_match": "UR",
  "bands_required": ["B02", "B03", "B04", "B08"],
  "band_rationale": "RGB for human-legible buildings; NIR helps separate bare construction surfaces from vegetation.",
  "predicate": "Have new buildings, roads, or other built-up features appeared, or existing ones been demolished, between the before and after tiles?",
  "fields": {
    "severity": {"type": "enum", "values": ["low", "moderate", "high", "extreme"]},
    "change_type": {"type": "enum", "values": ["new_construction", "expansion", "demolition", "mixed"]},
    "area_fraction": {"type": "number", "range": [0.0, 1.0]},
    "vlm_explanation": {"type": "string"},
    "confidence": {"type": "number", "range": [0.0, 1.0]}
  },
  "negative_output": null,
  "negative_instruction": "If the urban footprint looks unchanged, return null."
}