# fastapi.exceptions.RequestValidationError: field required

- **ID:** `python/fastapi-validation-error-field-required`
- **Domain:** python
- **Category:** type_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

A required field in the request body or query parameters is missing.

## Version Compatibility

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

## Workarounds

1. **Add default values or make fields optional** (90% success)
   ```
   class Item(BaseModel):
    name: str = 'default'  # optional with default
    price: float = 0.0
   ```
2. **Use Pydantic's Field with alias** (85% success)
   ```
   class Item(BaseModel):
    item_name: str = Field(..., alias='name')
# Request uses 'name', model uses 'item_name'
   ```

## Dead Ends

- **Providing field with None value** — FastAPI treats None as missing for required fields. (70% fail)
- **Using wrong field name due to case sensitivity** — Field names are case-sensitive in Pydantic models. (60% fail)