Graceful Degradation

# Graceful Degradation

Return partial results when full operation isn't possible.

## Category
Tool Resilience

## Context
Tools that aggregate from multiple sources or steps.

## Problem
Complete failure hides successful partial results.

## Solution
Degrade gracefully:
- **Return what worked**: Don't discard successes
- **Note what failed**: Explain gaps
- **Indicate completeness**: Partial vs full
- **Suggest remediation**: How to get the rest

## Example (Python)
```python
@tool
def get_unified_profile(user_id: str) -> UnifiedProfile:
    """Get user profile from multiple sources.
    
    Returns partial data if some sources fail.
    """
    profile = UnifiedProfile()
    errors = []
    
    try:
        profile.crm_data = crm_api.get_user(user_id)
    except Exception as e:
        errors.append(f"CRM unavailable: {e}")
    
    try:
        profile.email_data = email_api.get_user(user_id)
    except Exception as e:
        errors.append(f"Email service unavailable: {e}")
    
    profile.completeness = "full" if not errors else "partial"
    profile.errors = errors or None
    profile.retry_hint = "Call again later to get missing data" if errors else None
    
    return profile
```

## Considerations
- Always return something useful if possible
- Clearly indicate what's missing
- Provide retry guidance for missing parts

## Related Patterns
- partial-success
- scatter-gather-tool
- health-check

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Source: https://arcade.dev/patterns/graceful-degradation