# fastapi.exceptions.RequestValidationError: 1 validation error for Item
name
  field required (type=value_error.missing)

- **ID:** `python/fastapi-422-field-required`
- **Domain:** python
- **Category:** data_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

The Pydantic model declares a required field, but the incoming JSON body does not include it, so request parsing fails before the handler runs.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.x | active | — | — |

## Workarounds

1. **** (95% success)
   ```
   class Item(BaseModel):
    name: str = ''
   ```
2. **** (93% success)
   ```
   from typing import Optional
class Item(BaseModel):
    name: Optional[str] = None
   ```

## Dead Ends

- **** — Validation happens in FastAPI's dependency layer before the handler, so the except never triggers. (90% fail)
- **** — This affects output serialization, not input validation. (80% fail)