def explainability_report(results):
    agencies = {r["agency"] for r in results}
    exemptions = set()

    for r in results:
        exemptions |= set(classify_exemptions(r["snippet"])["codes"])

    return f"""
## System Explainability Report

**Purpose:** Public FOIA document discovery  
**Data Sources:** Public electronic reading rooms  
**Agencies Covered:** {', '.join(agencies)}

### Safety Controls
- Robots.txt enforcement
- Per-agency kill switches
- Redaction detection
- Exemption surfacing

### FOIA Exemptions Detected
{', '.join(exemptions) or 'None'}
"""